<u>Answer:</u> The unknown element X is calcium.
<u>Explanation:</u>
We are given:
An ionic compound having chemical formula = 
The given compound is a neutral compound and in a neutral compound, the oxidation states are exchanged.
We know that:
Oxidation state of chlorine ion = -1
So, the oxidation state of X ion will be +2
Atomic number is defined as the number of protons or electrons that are present in a neutral atom.
Atomic number = number of protons = number of electrons
Number of electrons = Number of protons - charge
We are given:
Mass number = 40
Number of electrons = 18
So, number of protons = Number of electrons + Charge
Number of protons = 18 + 2 = 20 = Atomic number
Hence, the unknown element X is calcium having atomic number '20'
Answer:
an endothermic reaction
Explanation:
An endothermic reaction has occurred.
Imaginary as there is no line
Answer:
radiometric dating
Explanation:
The age of rocks is determined by radiometric dating, which looks at the proportion of two different isotopes in a sample. Radioactive isotopes break down in a predictable amount of time, enabling geologists to determine the age of a sample using equipment like this thermal ionization mass spectrometer.
Hope this helps!
Answer: Velocity is the speed of an object plus its direction. Speed is called a scalar quantity and velocity is a vector quantity.
Explanation: hope this helps :)