For the last few days, we have discussed on the topics of “Acids, Bases & Salts” (Day 2 & Day 3). Today we are going to discuss a very basic but Important Sec 3 Chemistry Topic on “Atomic Structure“.
It is essential that all chemistry students must know this topic very well, in order to handle the rest of chemistry topics. Let’s look at some key points:
Atoms consists of 3 types of particles:
- Protons (+ve charge)
- Neutrons (Neutral)
- Electrons (-ve charge)
Protons and Neutrons are located inside the Nucleus of the atom while Electrons are arranged in Shells surrounding the nucleus. Each shell can hold a maximum number of electrons as shown below:
- Shell 1: 2
- Shell 2: 8
- Shell 3: 8
The electrons that are furthest away from the Nucleus is called the Outermost Shell Electrons or Valence Electrons. These electrons is very important because they are used to form Chemical Bonds.
- Metals tend to fewer outer shell electrons – 1, 2 or 3 electrons
- Non-metals tends to have many outer shell electrons
Number of Protons in an atom is called the PROTON NUMBER.
Number of Protons + Neutrons in an atom is called the NUCLEON NUMBER.
The number of Protons?= number of Electrons, and bcos of this, the +ve and -ve charges balance each other are all atoms are Neutral.
Isotopes is another important term you would need to know for GCE O Level Chemistry (also IGCSE, IB and IP Chemistry).
Isotopes are atoms of the Same Element with same number of Protons (and thus Electrons) but different number of Neutrons.
Isotopes have slightly different physical properties but have identical chemical properties because they have the same number and arrangement of Electrons.
Now, let’s try out some O Level Chemistry – type questions:
Question 1: Based on topic “Atomic Structure”
Which element has an isotope that does not contain neutrons?
a) Helium
b) Hydrogen
c) Neon
d) Nitrogen
and
Question 2: Based on topic “Atomic Structure”
An atom of Ne-20 loses two protons and two neutrons from its nucleus and forms the atom X.
a) What would be the number of protons and neutrons in the atom of X formed? (2 mark)
b) What is the symbol for X, including the proton and nucleon number? (1 mark)
and
Question 3: Based on topic “Atomic Structure”
What do the electronic configurations of the alkali metals (Group I elements on the Periodic Table) have in common? (1 mark)
Attempt the above questions and leave your answers and reasonings in the “Leave A Reply” section below.
Look forward to your participation. =)
PS: If you have any burning question that would like us to discuss on this humble chemistry blogsite, please do not hesitate to email us.
Stay tuned for the next post!
Neon-20. The isotope of neon which has a mass number of 20.
hey helium is in group 8 and has 2electron and how comes ya say has 20nucleon number,helium has 4nucleon number.hey guyz is nucleon number means mass number?
hey plz guyz can ya help me coz i dont understand in sadia comment how comes the atomic mass of 18electrons is 30.918 as far as i know is 36 and that element is argon and what about chemicai properties of atom and its ion is the same?
@sadia
Proton number of helium is not 20. 20 is its nucleon number. Lol.
Ans 1= Hydrogen because it has one proton and one electron but no neutron
Ans 2=Proton number is 20 after losing 2 protons,the number of protons will be 18
number of protons is equal to number of electrons so number of electrons will be 18
the number of neutrons
Ac nucleon no=30.918 proton no=18
no of neutrons =30.918-18 =12.918
Ans 3 = they have same valence shell s because they belong to group 1.they have same chemical properties also
Can you teach me how to read the Ne-20 ? i dont understand what does that mean. i havent learn this in school but i wanted to know. can you help me ? thankss. i like your site !
you are doing a good job.well done keep it up.plz send me o level’s solved papers