[He] 2s22p What is the chemical symbol for the atom?
How many electrons does the atom have?
How many 2s electrons are in the atom?

Detail is given below.

Explanation:

Electronic configuration:

[He] 2s² 2p⁵

Number of electron in given atom:

we know that the atomic number of helium is 2 it means it has 2 electron.

Thus the number of electron in given atom are 2+2+5 = 9

Symbol of atom:

The number of electron is the atomic number of an atom. Thus it means the given atom has atomic number 9 which is fluorine.

Symbol = F

Properties of fluorine:

1. it is yellow in color.

2. it is flammable gas.

3. it is highly corrosive.

4. fluorine has pungent smell.

5. its reactions with all other elements are very vigorous except neon, oxygen, krypton and helium.  

How many 2s electrons are in atom?

There are 2 electron are present in 2s subshell of fluorine.

specific gravity is the density of a substance divided by the density of water. since (at standard temperature and pressure) water has a density of 1 gram/cm3, and since all of the units cancel, specific gravity is usually very close to the same value as density

so "c" is the answer

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