Which pair of atoms is held together by a covalent bond hcl licl nacl kcl

HCL

Explanation:

Covalent bond are formed between non metals so look for the pair of non metal atoms and this would be hydrogen chloride (HCL)

out of these options:

ability to burn paper

pure sodium reacting violently with water

the boiling point of water

helium does not tend to react with anything

i would say this is a physical property:

helium does not tend to react with anything

why? :

i said helium does not tend to react with anything because well, it reacts to ! but ability to burn paper, pure sodium reacting violently with water, & the boiling point of water are chemical or

physical properties: the properties of a substance that can be observed without changing the chemical makeup of the substance

chemical properties: properties of a substance relating to the chemical nature and reactivity of the substance

6.4 cm (max) - 25 cm (min)