(i) 1s2 2s2 2p6 3s1 (ii) 1s2 2s2 2p6 3s2 (iii) 1s2 2s2 2p6 3s2 3p1 (iv) 1s2 2s2 2p6 3s2 3p4 (v) 1s2 2s2 2p6 3s2 3p5 the electron configuration of the atom that is expected to have a positive electron affinity is

V

Explanation:

Firstly let’s list the names of the atoms

1. Sodium

2. Magnesium

3. Aluminum

4. Oxygen

5.Chlorine

Generally, anions have greater electron affinity than cations. Hence, they have more positive values for this electron affinity. This means that the higher the electron affinity, the greater its positive value

Electron affinity increases across a period. Thus, it is expected that chlorine has the highest value

108

explanation:

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explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.