How do valence electrons affect chemical bonding?

Valence electron determines which type of how bonding will take place...

If the atom have 1 valence electron then, it can be form ionic bond with the atom who has 1 electron vacant... If atom has 4 electron in the valence shell, then it will be form covalent bond

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

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since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante