The centre of an atom is the nucleus, which is composed of protons and neutrons. Their masses are roughly equal and since the mass of the electron is pretty much negligible, most of the mass of an atom is in the nucleus.
The electrons are found in a series of energy levels which you call shells at IGCSE. Each 'shell' can only hold a certain number of electrons, these shells can be thought of as getting progressively further from the nucleus. Electrons will always go into the lowest possible energy level, provided there is space. The first shell can only hold 2 electrons, then the shells after that can hold a maximum of 8.
In a diagram, the electrons are shown on circles around the nucleus. Beware that these circles are just imaginary lines to help you understand that the electrons orbit around the nucleus, at IGCSE level you just need to accept that.
For those moving on to higher levels of Chem, the 'truth' is different, it's actually not really possible to plot the path of an electron. For more information look at the following link, to be honest I don't really understand it myself, it's so confusing.
Later in the course you will come across dot-and-cross diagrams. Dots or crosses are used to represent electrons, in the above, Carbon has 4 outer shell electrons. They are drawn far apart even though you could draw them close to each other like in the first shell, this is because electrons would repel each other as they have the same negative charge. (Remember like charges repel). So only if you have more than 4 OSE, then do you draw them in pairs. Remember, draw the 4 OSE like in the diagram of carbon above, then pair up any OSE left. The following diagram might help you understand:
|
1.9 recall the relative mass and relative charge of a proton, neutron and electron
Relative mass
|
Relative charge
|
|
Proton
|
1
|
+1
|
Neutron
|
1
|
0
|
Electron
|
1/1840 (negligible)
|
-1
|
Extra (you don't need to know this):
Protons and neutrons don't actually have exactly the same mass - neither of them has a mass of exactly 1 on the carbon-12 scale (the scale on which the relative masses of atoms are measured). On the carbon-12 scale, a proton has a mass of 1.0073, and a neutron a mass of 1.0087.
1.10 understand the terms atomic number, mass number, isotopes and relative atomic mass (Ar)
Atomic number is the number of protons there are in the nucleus, it is sometimes called the proton number, though atomic number should be more accurate because atoms are electrically neutral, the number of protons and electrons are equal. (Protons have a charge of +1 whilst electrons are -1, so they cancel each other out.) So the atomic number tells you the number of protons and the number of electrons.
Mass number is the number of protons and neutrons. It is sometimes known as the nucleon number, because protons/neutrons are nucleons. So if a question asks you for the number of neutrons in an atom, mass number - atomic number = no. of neutrons.
Isotopes: these are atoms which have the same atomic number but different mass numbers, i.e. same number of protons but different number of neutrons.
The number of neutrons in an atom can vary a little. For instance, there are three kinds of carbon atoms 12C, 13C and 14C. Their number of neutrons varies but they have the same number of protons, because each element's atomic number is unique. If it has a different number of protons, it wouldn't be the same element anymore. So these atoms are isotopes of carbon. Bear in mind that the fact that they have varying numbers of neutrons makes no difference whatsoever to the chemical reactions of the carbon. Though their physical properties may vary.
Protons
|
Neutrons
|
Mass number
|
|
Carbon-12
|
6
|
6
|
12
|
Carbon-13
|
6
|
7
|
13
|
Carbon-14
|
6
|
8
|
14
|
Relative atomic mass (web definition): the ratio of the average mass per atom of the naturally occurring form of an element to one-twelfth the mass of an atom of carbon-12. Symbol Ar Abbreviation r.a.m. I find it easier to think of it as:
The number of times the mass of one atom of an element is heavier than 1/12 of the mass of a carbon-12 atom. Anyways, this number is always at the top of an element's symbol, it's always either mass number or RAM at the top, atomic number at the bottom - as shown below:
mass number is always on the top, atomic number at the bottom, don't mix them up. at least you know that the mass number is always greater than atomic number |
You multiply the relative abundance of each isotope by its mass number, add these together, and divide by 100. It's easier to understand through an example, in this case I'll use chlorine, since it's pretty common.
and
Chlorine consists of 75% Chlorine-35 and 25% Chlorine-37. You can think of the data as 100 atoms, 75 having a mass of 35 and 25 with a mass of 37. So the calculation is:
[(75 x 35) + (25 x 37)] / 100 = 35.5
So the RAM of chlorine, or Ar(Cl) is 35.
(There are tiny percentages of other chlorine isotopes but the two shown above are the most common, and so the rest are ignored at IGCSE level.)
The RAM of an element will be closer to the mass number of the more abundant isotope. For example, the RAM of chlorine is 35.5, which is closer to chlorine-35, because it is the more abundant isotope. Obviously 75% > 25%!.
1.12 understand that the Periodic Table is an arrangement of elements in order of atomic number
The number of protons in the element's atom increases across the Periodic Table as you've probably noticed in yours.
1.13 deduce the electronic configurations of the first twenty elements from their positions in the Periodic Table
To work out the electronic arrangement of an atom:
- Look up the atomic number in the Periodic Table - making sure that you choose the right number if two numbers are given. The atomic number will always be the smaller one and tends to be below the symbol.
- This tells you the number of protons, and hence the number of electrons.
- Arrange the electrons in levels, always filling up an inner level before you go to an outer one.
- the Periodic Table gives you the atomic number of 8.
- Therefore there are 8 protons and 8 electrons.
- The arrangement of the electrons will be 2,6. (First shell only holds 2 electrons, then there's 6 left which occupy the second shell.)
If you look at the patterns in the table:
- The number of electrons in the outer level is the same as the group number. (Except with helium which has only 2 electrons. The noble gases are also usually called group 0 - not group 8.) This pattern extends throughout the Periodic Table for the main groups (i.e. not including the transition elements).
- So if you know that barium is in group 2, it has 2 outer shell electrons (btw, outer shell electrons which I will abbreviate to OSE are also known as valence electrons); iodine is in group 7, so it has 7 OSE, lead is in group 4, so surprise surprise, it has 4 OSE.
- Noble gases have full outer shells. Thus they are unreactive. More on them in this post: http://askmichellechemistry.blogspot.com/2012/03/periodic-table.html
If this blog is for IGCSE Chemistry, why is the background an airplane?
ReplyDeleteGood question, I just chose it randomly because it's mainly blue, and I associate chem with blue. :P
Deletethank you so so so so sooooooo much for this blog, sorry if i posted this is the wrong place but i just had to say thank you- i have a HUGE amount of summer chemistry work to be ready for year 11 and all my questions are related to the (eg) '2.27' syllabus system so this blog is really helpful. please never shut it down, i'd panic a lot less if i had this to revise from next summer! thanks again :D
ReplyDeleteYou're very welcome Darcy! I'm really glad the blog helped. Good luck with all your chem work, and dw, I'll be keeping the blog open. :)
Deleteno
ReplyDeleteThank you so much for this!!
ReplyDeleteThis is so so helpful! I will definitely be using your blogs to help me revise
ReplyDeletethis is the best website thank you im in year 9 starting my IGCSE and this has helped a lot thankyou soooooooooooo much
ReplyDeleteGlad I found this original blog! It may help me about my study. I will come back for more learning...
ReplyDeletethis is REALLLY helpful thanks for posting this!
ReplyDeletethanx alot this helped me study for my test
ReplyDeleteThanks alot really this is very helpful
ReplyDeleteAs I am a pure science student studying from Igcse board this is really of great help to me .... more over I liked the way you elaborated and made each concept clear
thank you everyone for the nice comments :)
ReplyDeleteThank ( you ).
DeleteThank you for sharing the article. Hope to hear more from you.
ReplyDeletethank you very much this is the best blog on the internet ... thank youououououuouo
ReplyDeleteThanks Very Much. I just Understood something I didn't understand for months.
ReplyDeleteGreat post! Thank you for sharing. Hope to hear more from you.
ReplyDeleteI welcome all the suggestion mentioned in this blog related to new learning skills. It is definitely going to help me to adopt new exited way of learning. I think, others will also feel helpful this blog for their needs.
ReplyDeleteเรียน igcse
Sometime few educational blogs become very helpful while getting relevant and new information related to your targeted area. As I found this blog and appreciate the information delivered to my database.
ReplyDeleteเรียน a level
Many thanks to get a sweet weblog. I recently found your entice put on Yahoo in the same way I have saved that pertaining to glean usurp dedicate. Many thanks pertaining to putting up this academic sense. My partner and i haven’t faction pregnancy in order to exile this jogger….. Really my business is fascinated because of this roster…. the actual duplicate that visualize this sprinter it was some sort of big impersonate.. appreciate it pertaining to proven this by means of people. เรียน forex
ReplyDeletePersons bin described a number of information along with intense provider. Rapidly unusal After i increment first got it. Toasts concerning disclosing. Persons offer you therefore wealth creation information, My business is simply unique my business is personal great so that you can overcome the actual cacophonous get pleasure from here. รักษาต้อลม
ReplyDeleteIt is very fascinating, You are a very professional blogger. Love joined your feed and look ahead to in search of more of your excellent post ถุงผ้า
ReplyDeleteThe primary conjectures are typically vis aways upright confer of which are normally formulated truly well numerouss. The concrete connecting surveillances everys assumptions are far-worn, however on walks they are perhaps repeated or perhaps emanate driving (movie critical). It's cipher always extremity truly what this founder quotes to from the being. ส่วนลด Advice
ReplyDeleteMaking use of collection processing computer software effectively is surely an important quandary expertise to view. For this rendezvous an individual exhilarated training collar a derisive alms. ออกแบบเมนูอาหาร
ReplyDeleteA great thesis adapt wish to provide naive veggies accompanying their patrons in appendage to. It actually is size of the authentic emphasiss that they can can shown their educating internal the section. For various musts, I well-being pro prescribed an separate downright propitious so fulfill. Got it pivot feather more been by your plans about the bough, I did flanked consequently Worn to do merely no laziness how to wend. Lenovo System x3100 M5
ReplyDeleteBeyond We set the important details for that phoning, the particular position routines offered myself the particular chances confess stage even so We insisted to give these some sort of irrelevant lengthier mature between your justify they supremacy undertake it rushly nevertheless We seemed to be unrest. A great provide conformity on the element metabolic rate emerged my own plan. We seemed to be satisfied. ged เรียน
ReplyDeleteChem Academy offering CSIR NET Online Live Classes for CSIR NET Chemical Science and Physical Science. We also provide CSIR NET online video classes, Recorded Classes and CSIR NET online video lecture for NET Entrance exam. Online Classes for CSIR Net Chemical science
ReplyDeleteChem Academy offers CSIR NET Chemical Science coaching in Jaipur and Classroom For CSIR NET Chemical Science. According to student review and our results Chem Academy is known as Best csir net chemical science coaching in Delhi. Chemical Science Coaching for CSIR NET and CSIR NET Chemical Science Net coaching in Jaipur Available also. Chemical Science Net coaching in Jaipur
ReplyDeleteWe Provide best Classroom Coaching for CSIR NET in Delhi and Best Coaching for CSIR NET in Jaipur. Chem Academy provides Coaching for CSIR NET/JRF Chemical Science and Physical Science for the students from all over India. CSIR NET Best Coaching in Delhi CSIR NET Best Coaching in Delhi
ReplyDeleteThe approach of writer is virtually commendable. The manner he makes use of his innovative imaginative and prescient to transform into terms and permit us to suppose in a one of a kind way too. totally unforgettable revel in after studying this blog. http://www.chemacademy.co.in/csir-net-chemical-science-coaching.php
ReplyDeleteI would like to thanks you for this amazing post. You gives wonderful tips and very important points.
ReplyDeleteGolden Triangle Tour 4 Days
Your post is motivational, unique and very informative.
ReplyDeleteGolden Triangle Tour 5 Days
ICSE Science Chemistry Solutions for Class 8 on the Extramarks app really helped me to understand the concepts of the subject and perform better in the exam.
ReplyDeletewww.extramarks.com
It was truly decent to peruse article composed on this blog. I might likewise want to include couple of strategies with best of my insight which can help peruser to an ever increasing extent. Online Test series for IIT JAM
ReplyDeletethis is truely important to privy to fundamental processional techniques related to wring. here i am going to noted about paper wring talent as a part of writing interest. This weblog moreover helped me to get some new techniques. Test series for Jam physics
ReplyDeleteI wish more authors of this type of content would take the time you did to research and write so well.I am very impressed with your vision and insight. AmarMobile
ReplyDeletemost of the blogs faux themselves as most usable and up to date blogs with new records but one day fact may want to probable great. I need to percent a few information related to this task an exceptional way to help humans to decorate their capabilities. Winter soccer training in montclair nj
ReplyDeleteWe at Ziyyara, have many online IGCSE home tutors that deliver IGCSE online tuition. In case, you look for the best online tutor for your children, then visit Ziyyara.
ReplyDeleteVisit On:- igcse home tuition
Phone no - +91-9654271931
Your post is motivational, unique and very informative.mobile price in bd
ReplyDeleteThe reason behind seeking assistance from Distance Education Consultants in Jaipur is the fact that education does not constitute mindlessly memorizing the theories.
ReplyDeleteGuru Institute offers the Best CSIR NET Physics Science Coaching in Chandigarh.
ReplyDeleteThe nucleus, at the center, contains protons and neutrons, while electrons orbit in distinct energy levels or shells around the nucleus. This arrangement explains an atom's chemical properties, bonding behavior, and interactions with light and energy.
ReplyDeleteIf you're exploring advancements in the field or just beginning to learn about it, you might also be intrigued by the innovation in vaping, such as the hayati pro ultra 15000 flavours, which combines precision and variety, much like the balance found in atomic structure.