Which is the correct sequence of transferring heat through convection?
1. As a result, the heated part becomes less dense or lighter.
2 The colder air above us is denser and heavier so it goes
down and pushes the hot air upward.
3 The cold air is pushed upward by colder heavier air above. In
this way, the entire liquid or gas becomes evenly heated.
4 When liquid or gas is heated the molecules of the heated part
move faster and faster away from each other.​

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.