Number of neutrons = mass number - atomic number = 40 - 19 = 21 answer
This means the nucleus of an atom is always positively charged
a compound in chemistry, is any substance that is formed when two or more chemical elements are chemically bonded together. A prime example of this is H20. You are combining hydrogen to oxygen, giving you a compund element. I hope this helps you. :)
Answer:
it is less dense than oxygen gas.
Explanation:
Hydrogen is the simplest chemical element that exists. The symbol for the chemical element Hydrogen is "H" and it is a colourless, tasteless, odorless, and highly flammable gas.
Hydrogen is a chemical element found in group (1) of the periodic table and as such it has one (1) electrons in its outermost shell. Therefore, Hydrogen has an atomic number of one (1) and a single valence electrons because it has only one proton and one electron in its nucleus.
In Chemistry, the properties of a chemical element that can be observed and measured without changing its chemical nature is known as a physical property. It includes density, color, freezing point, opacity, smell, melting point, viscosity, etc.
Hence, the statement which describes a physical property of hydrogen is that it is less dense (density) than oxygen gas.
