UNIT-1

Question 1

Define the term nucleus?

Answer 1

Small, dense protons and neutrons.

Question 2

Define the term electron cloud?

Answer 2

Region of space where there is a probability of an electron being found.

Question 3

What is a compound?

Answer 3

Are substances that are made up of more than one type of atom or element.

Question 4

What is the rule for the absolute maximum number of covalent bonds an atom can make? [Using example of (S) atom.]

Answer 4

It is equal to the number of valence electrons in that atom. For example (S) has an electronic configuration (2,8,6) so it can form a maximum of 6 covalent bonds.

Question 5

What does a higher core charge mean?

Answer 5

The higher the core charge, the greater the attractive force of the atom on the external atom, and therefore the higher the electronegativity.

Question 6

Electronegativity increases or decreases across a period?

Answer 6

Increase across a period.

Question 7

Electronegativity increases or decreases across a group?

Answer 7

Decreases across a a group.

Question 8

What does greater distance of the valiance shell from the nucleus mean?

Answer 8

The greater the distance of the valiance shell from the nucleus, the less attractive the attractive force of the core towards the external electron and therefore lower the electronegativity.

Question 9

Electronegativity is determined by?

Answer 9

Core charge and distance of the valiance shell from the nucleus.

Question 10

Summarize the difference between an atom in its ground state and a atom in its excited state?

Answer 10

An atom in the ground state have electrons that occupy the lowest possible energy state while an atom in the excited state has electrons that are not. Atoms enter the excited state when they absorb energy and an electron moves from a lower energy level to a higher energy level.

Question 11

The electronic configuration of 5 elements are show below:
A 1s^2 2s^2 2p^6
B 1s^2 2s^1
C 1s^2 2s^1 2s^6
D 1s^2 2s^2 2p^6 3s^2 3s^6 3s^8 4s^2
E 1s^2 2s^2 2p^6 3s^2 3s^4

a) From the list of the elements, write the letter of the element which:
i) is in an excited state
ii) is in group 1
iii) would be found in group 6
iv) would form an ion with a -2 charge
v)has the same electron configuration as Na+

b) The periodic table developed by Mendeleev (c.1869) was based on placing the known elements in increasing order of atomic mass. On what basis is the modern periodic table based.

Answer 11

i)c
ii)b
iii)e
iv)e
v)a
b) In order of increasing proton number with elements with the same number of outer shell electrons placed in the same group.