Describe the motion of molecules in these two substances when the ice cube is placed on the radiator.

When in direct contact, the fast-moving molecules in the radiator collide with the slow-moving molecules in the ice cube.

Kinetic energy is transferred from the molecules in the radiator to the molecules in the ice cube, causing a slowdown of the radiator molecules and an acceleration of the ice molecules.

Explanation:

it's c. elements are placed in rows based on how may valencies electrons have.

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.

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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.