Answer:
NaF
Explanation:
This is basic, NaCl is neutral, and the others are acidic.
A element, because they are identically physically and chemically.
Answer:

Explanation:
The atomic weight of oxygen = 15.9994 g
This mass corresponds to 1 mole of the oxygen atoms.
Thus,
15.9994 g mass of oxygen contains
atoms of oxygen.
1.4 kg = 1400 g ( 1 kg = 1000 g)
So,
1400 g mass of oxygen contains
atoms of oxygen.
Number of atoms in 1400 g of oxygen = 
Also, 1 atom of oxygen contains 8 protons
Charge of 1 proton = + 
So, Charge on 1 atom of oxygen = 
Thus,
Charge on
atoms of oxygen = 
Thus, positive charge in 1.4 kg of oxygen = 
Explanation:
The group number in the periodic table represents number of valence electrons of the elements in a certain group.
Group 1 : 2,8,1
Group 2 : 2,8,8,2
Group 3 : 2,8,3
Group 4: 2,4
Group 7 : 2,8,7