Answer:
(1) atomic numbers
Explanation:
The observed regularities in the properties of the elements on the periodic table are periodic functions of their atomic numbers.
- Atomic number is the number of protons in an atom.
- The periodic law states that "the properties of elements are a periodic function of their atomic number".
- Elements on the periodic table are arranged based on the atomic numbers they contain.
- The number of positively charged particles in an atom is the atomic number.
Answer:
c. Cr
Explanation:

The compound is containing
ion.
If acid reacts with it, CO_2 evolves.

therefore, Cr would form a precipitate when added to an aqueous solution of this compound. Cr2CO3 is the precipitate.
The ideal gas law:

p - pressure, n - number of moles, R - the gas constant, T - temperature, V - volume
The volume and temperature of all three containers are the same, so the pressure depends on the number of moles. The greater the number of moles, the higher the pressure.
The mass of gases is 50 g.

The greatest number of moles is in the container with Ar, so there is the highest pressure.