1. Atoms are mostly empty space
2. Atoms have a concentration of positive matter somewhere in them
3. The concentration of this positive matter is very small
Answer:
Number of neutrons: 44
Number of protons: 34
Number of electrons: 36
Explanation:
The atomic number of Se (Selenium) is 34
Mass number is 78
Number of neutrons = mass number - atomic number = 78 - 34 = 44
Number of protons is the same as the atomic number
Number of protons = 34
Selenium ion has a charge of -2. This means it accepts two more electrons
Number of electrons = atomic number + 2 = 34 + 2 = 36
States that the properties of elements are periodic or recurring and are correlated to their atomic number.
