Question

please answer questions no 9 fast .........

Answer 1

Atomic no. of X is 5

Mass no. of X is 11

Valency of X is 3

Atomic no. of Y is 8

Mass no. is 18

Valency is 2

Atomic no. of Z is 15

Mass no. is 31

Valency is 3

Answer 2

first figure resembles distribution of electrons in boron.it's has 5 protons it's atomic number is 5.it has 6 neutrons. so the atomic mass is protons + neutrons. hence the atomic mass is 11. it has 3 electrons in its outermost shell so it's valency is 3.
similarly,second one electronic distribution of oxygen.it's atomic number is 8 because it has 8protons.it has 10 neutrons so it's atomic mass is 18.it's valency is 2 because it has 6 electrons in its outermost shell so it needs 2 electrons to become stable or to gain octet.hence valency is 2.
similarly last one is phosphorus.it atomic number is 15 and it's mass is 31 and valency is 3.