Chapter - 4 The Periodic Table
1. Answer the questions that follow using only the elements in this list:
caesium, chlorine, molybdenum, neon, nickel, nitrogen, strontium, tin.
a) State the name of an element which is:
(i) in Group 2
(ii) in the same period as silicon
(iii) in the same group as phosphorus
(iv) in Period 6
(v) a noble gas
b) Divide the list of elements at the beginning of the question into two groups, metals and
non-metals.
Ans : a) (i) Strontium.
(ii) Chlorine.
(iii) Nitrogen.
(iv) Caesium.
(v) Neon.
Ans : b)
Non-Metals
Metals
Caesium
Chlorine
Molybdenum
Nickel
Nitrogen
Strontium
Tin
2. Draw diagrams to show the arrangement of the electrons in:
a) sodium
b) silicon
c) sulfur
Neon
Ans : a) 11Na -> 2,8,1
b) 14Si -> 2,8,4
c) 16S -> 2,8,6
3. State the electronic configurations of the following atoms:
a) fluorine
b) aluminium
c) calcium
Ans : a) 9F -> 2,7
b) 13Al -> 2,8,3
c) 20Ca -> 2,8,8,2
4. Find each of the following elements in the Periodic Table and state the number of electrons in its outer
shell:
a) arsenic, As
b) bromine, Br
c) tin, Sn
d) xenon, Xe
Ans :
Element
a)
Periodic Number
Arsenic (As)
Group
4
5
b)
Bromine (Br)
c)
Tin (Sn)
d)
Xenon (Xe)
4
7
5
4
5
8
5. The questions refer to the electronic configurations below. Don’t worry
if some of these are unfamiliar to you. All of these are the electronic
configurations of neutral atoms.
A 2, 4
B 2, 8, 8
C 2, 8, 18, 18, 7
D 2, 8, 18, 18, 8
E 2, 8, 8, 2
F 2, 8, 18, 32, 18, 4
a) Explain which of these atoms are in Group 4 of the Periodic Table.
b) State which of these electronic configurations represents carbon.
c) Explain which atoms are in Period 5 of the Periodic Table.
d) Explain which of these electronic configurations represents an element in Group 7 of the Periodic
Table.
e) State which of these electronic configurations represent noble gases.
f) State the name of element E and explain how you arrived at your answer.
g) State how many protons are present in an atom of element F. State the name of the element.
h) Element G has one more electron than element B. Draw a diagram to show how the electrons are
arranged in an atom of G.
Ans : a) A and F. Contains four electrons in it's outershell.
b) A. Atomic Number of Carbon is 6.
c) C and D. Both have five electron shells.
d) C. Outer shell contains seven electrons.
e) B and D, because outer shell is full.
f) Calcium. Atomic number of Calcium is 20. Calcium is in group 2 and period 4.
g) F has 82 protons.
F -> Lead (Pb)
h) B -> 2,8,8
G -> 2,8,8,1
6. Predict two properties of the element palladium, Pd (atomic number 46), or its compounds. The
properties can be either physical or chemical.
Ans : Palladium is a transition metal.
Properties of transition metal are : 1) High Melting Point.
2) High Density.
3) Good conductor of electricity.
4) Good Catalyst.
5) Variable valency.
6) Forms basic oxide.
7. Helium and neon do not form any compounds. Explain why the noble gases are unreactive.
Ans : He -> 2
Ne -> 2,8
In Helium (He) and Neon (Ne) outer shell is full, they neither take or give electron to form compounds.
Therefore, Helium and Neon are noble gases and are unreactive.
8. The elements in the Periodic Table are arranged in order of atomic number. If they were arranged in
order of mass number give the names of two elements that would be in different positions. Explain why
this would cause a problem.
Ans : Name of two elements :
Potassium -> 3919K
Argon -> 4018Ar
In Argon (4018Ar), there are 18 protons and 22 neutrons.
In Potassium (3919K), there are 19 protons and 20 neutrons.
The elements would then be in a different group in the Periodic Table. They would not have the same
number of electrons in the outer shell as other members of the group and would react in a completely
different way. For example, potassium would be in Group 0 with the noble gases and argon which is very
unreactive would be in Group 1, with the highly reactive alkali metals.