Elements A, B,C and D have atomic numbers 11,18,1 and 17 respectively. Give the chemical formulae of the compound formed between: a) A and D
b) B and C

a ) NaCl

b) No compound.

Explanation:

Atomic number of A is 11 , thus it is sodium. It has electronic configuration of 2,8,1 and thus has 1 valence electron and can form .

Atomic number of B is 18 , thus it is argon. It has electronic configuration of 2,8,8 and thus it is an inert gas.

Atomic number of C is 1 , thus it is hydrogen. It has electronic configuration of 1. It can only share electrons.

Atomic number of D is 17 , thus it is chlorine. It has electronic configuration of 2,8,7 and thus has 7 valence electron and can form .

a) A and D :

Here Sodium is having an oxidation state of +1 called as cation and anion is . Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral

b) B and C

As B is an inert gas , it wont combine with C.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.