Question

2. The electronic configuration of three elements X, Y and Z are given below.
X = 2:
Y = 2, 6;
Z = 2, 8, 2.
a) Which element belongs to the second period?

b) Which element belongs to the eighteenth group?

c) Which element belongs to the second group?

d) What is the valency of Y?

e) Are Y and Z metals or non-metals?
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Answer 1

Answer:

a) Y belongs to the second period as it has 2 shells.

b) X belongs to the eighteenth group as it has attained noble gas configuration because its outermost shell is full.

c) Z belongs to the second group as it has 2 valence electrons.

d) The valency of Y is 2 as it has to gain 2 electrons to attain noble gas configuration.

e)Y is a non-metal as it's easier for it to gain 2 electrons to attain noble gas configuration and Z is a metal as it's easier for it to lose 2 electrons to do the same.

Answer 2

X belongs to the 18th group. Z is a metal and belongs to the 2nd group. Y is a non-metal and belong to the 2nd period and has a valency of 2.

• The highest quantum number in the electronic configuration of the elements helps to identify the period of that particular element.
• The electronic configuration of
• X = ${1s}^{2}$
• Y = ${1s}^{2} {2s}^{2} {2p}^{4}$
• Z = ${1s}^{2} {2s}^{2} {2p}^{6} {3s}^{2}$
• So, the period number of X, Y, Z are 1, 2, and 3 respectively.
• As we know that noble gases belong to eighteen groups and also noble gases have stable electronic configuration i.e their outermost shell is full and there is no need of gaining or losing electrons. Here, X has the stable electronic configuration so, it belongs to the 18th group.
• The elements of s-block belongs to the 2nd group. Here, Z is the element that belongs to the s-block and as the subscript over the last alphabet is 2 that means Z belongs to the 2nd group.
• As Y can gain two electrons and by doing so it can attain a stable configuration so, the valence of Y is 2.
• Non-metals are the elements that gain electrons to attain a stable configuration while metals are the elements that lose electrons to attain a stable configuration. Here, Y and Z are the elements that can gain and lose 2 electrons respectively to attain a noble configuration.

Hence, Y is a non-metal and belong to the 2nd period and has a valency of 2. Z is a metal and belongs to the 2nd group. X belongs to the 18th group.