<span>H2S has 2 bonds which means that it has two shared electron pairs. It has 2 lone pairs on electrons. It's the only one where the 2 are the same.</span>
The universe comes into existence is first
The first neutral atoms form is second
The universe begins expanding is third
Gases form that will later go to shape stars and galaxies is fourth
Atomic nuclei form is last
I'm almost certain that is correct. Do not take my word for this.
<u>Answer:</u> The correct answer is the mass number of the most common isotope of the element is 24.
<u>Explanation:</u>
We are given:
An element having atomic number 12 is magnesium and atomic mass of the element is 24.305
The image corresponding will be 
The number '24.305' is the average atomic mass of magnesium element.
Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.
Formula used to calculate average atomic mass follows:

Average atomic mass of magnesium = 24.305 amu
As, the average atomic mass of magnesium lies closer to the mass of Mg-24 isotope. This means that the relative abundance of this isotope is the highest of all the other isotopes.
The 'Mg-24' isotope is the most common isotope of the given element.
Hence, the correct answer is the mass number of the most common isotope of the element is 24.
Answer:
Ionic bond is formed by the opposite ions attraction between the 2 atoms in an ionically bonded compound. The two ions i.e. Cation and Anions are formed by oxidation and reduction reactions respectively. General Ionic formula is as follow,
Mⁿ⁺ + Nⁿ⁻ → MN
where;
Mⁿ⁺ = Cation
Nⁿ⁻ = Anion
MN = Salt
Explanation:
Ionic bond is the electrostatic forces of attraction between positively charged cations and negatively charged Anions. These forces are very stronger resulting in increasing several physical properties of Ionic compounds like melting point and boiling point e.t.c.
Example:
Sodium Chloride:
NaCl is formed by Na⁺ cation and Cl⁻ anion as follow,
Oxidation of Na;
2 Na → 2 Na⁺ + 2 e⁻
Reduction of Cl₂;
Cl₂ + 2 e⁻ → 2 Cl⁻
Crystal Lattice formation is as follow,
Na⁺ + Cl⁻ → NaCl