An atom X has a proton number of 19 and relative atomic mass of 39. (i) How many electrons, protons and neutrons are there in an atom of X?

(ii) How many electrons will there be in the outer energy level (shell) of an atom of X?

(iii) What is the electronic configuration of X?

(i)electrons = 19; Protons = 19 Neutrons =39-19=20

(ii) 1

(iii) 2,8,8,1

Hope this helps.

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you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6