I am pretty sure the answer is . But I might be wrong.
Phosphorus has 16 neutrons. Phosphorous is 15 on the periodic table, which means that the atomic number (number of protons) of phosphorous is 15.
For more info: https://study.com/academy/answer/what-is-the-number-of-neutrons-in-phosphorus.html
Explanation:
12)
a) Sodium + oxygen = ?
When sodium reacts oxygen its forms sodium oxide as a product.

b) magnesium + fluorine = ?
When magnesium reacts with fluorine its forms magnesium fluoride as a product.

13)
a) 
Decomposition of mercury(II) oxide on heating gives out mercury and oxygen gas.
b)
The electrolytic decomposition of water gives out hydrogen gas amd oxygen gas.
Answer:
- Compress
- Fixed
- Melts
- Melting Point
- Freezing Point
- High
- Crystalline
- Lattice
- Unit cell
- Amorphous solids
Explanation:
Solids tend to be dense and difficult to <u>compress.</u>
They do not flow or take the shape of their containers, like liquids do, because the particles in solids vibrate around <u>fixed</u> points.
When a solid is heated until its particles vibrate so rapidly that they are no longer held in fixed positions, the solid <u>melts</u>.
<u>Melting point</u> is the temperature at which a solid changes to a liquid. The melting and <u>freezing point</u> of a substance are at the same temperature.
In general, ionic solids tend to have relatively <u>high</u> melting points, while molecular solids tend to have relatively low melting points.
Most solids are <u>crystalline</u>
The particles are arranged in a pattern known as a crystal <u>lattice</u>
The smallest subunit of a crystal lattice is the <u>unit cell</u>
Some solids lack an ordered internal structure and are called <u>amorphous solids.</u>