Answer:
b,c,d
Explanation:
gasses exert pressure, all particles of a gas sample move at the same speed. gas particles can exchange kinetic energy when they collide.
When studying atoms, scientists can ignore <u>the Gravitational</u> force between charged particles that make up the atoms because it is many millions of times smaller than other forces in the atom.
Explanation:
Scientists can ignore the gravitational force because the gravitational force is considered to be negligible as compared to the other forces due to its smaller value.We all know that the gravitational force is directly proportional to the mass of an object which result in a small force value.When the value of this small force is compared to the value of the electrical force between protons and electrons in atoms the we can say that the electrical force is million times stronger than the gravitational force
Thus we can say that scientists can ignore <u>the Gravitational</u> force between charged particles that make up the atoms because it is many millions of times smaller than other forces in the atom.
Answer: Option (d) is the correct answer.
Explanation:
A reaction in which there occurs change in oxidation state of reacting species is known as an oxidation-reduction reaction.
(a)
Will be written as:

In this reaction, there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.
(b) 
Will be written as:

Similarly here, there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.
(c) 
Will be written as:

Here, also there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.
(d) 
So, here there occurs change in oxidation state of Mg from 0 to +2 and oxidation state of H changes from +1 to 0. Hence, it is an oxidation-reduction reaction.
Thus, we can conclude that
is an oxidation-reduction reaction.
Na5Cl2
penta is 5, so 5 sodiums and di is 2, so 2 chloride