1. What is the total number of neutrons in a nucleus of magnesium-23?
A. 23
B. 11
C. 12
D. 16
_______2. The periodic law states that there is periodic repetition of the physical and chemical properties of elements ________
A. when they are arranged in order of increasing atomic mass.
B. if only metals are considered.
C. when they are arranged in order of increasing atomic radii.
D. when they are arranged in order of increasing atomic number.
_______3. How many positively charged particles do 2145 have?
A. 21
B. 45
C. 24
D. 66
_______4. How many negatively charged particles do 2145 have?
A. 21
B. 45
C. 24
D. 66
_______5. Dmitri Mendeleev organized the chemical elements:
A. by number of electrons
B. by increasing atomic mass and similar properties
C. by increasing atomic number and similar properties
D. in alphabetical order​