Particle Physics

No need, just for convenience. Eg the mass of an electron is 9.11*10^-31 kg = 8.19*10^-14 J/c^2 = 512000 eV/c^2.

Which is the easier number to work with? The mass in kg or J/c^2 which is so tiny you can't really grasp it (and it makes maths trickier, you've got to remember to keep all those powers of 10) or the mass in eV/c^2.

An atom of 21Ne has 11 neutrons. This is determined by subtracting the atomic number (which is 10 for neon) from the atomic mass number (which is 21 in this case).

Neutrons are not the lightest subatomic particles. Electrons are the lightest subatomic particles, with a much smaller mass than neutrons. The mass of a neutron is approximately 1839 times that of an electron.

The photoelectric effect, where light can knock out electrons from a material, provides evidence of light behaving as a particle. Additionally, experiments showing the diffraction and interference of light can be explained by considering light as a stream of particles called photons. The Compton effect displayed by X-rays scattering off electrons also supports the particle nature of light.

There's no actual evidence that quarks are not fundamental particles, so as far as we know there's nothing inside them, they just are. There are a couple of half-baked theories that quarks are actually made of "strings" or "preons" (on the scale from "crackpot" to "fully validated scientific theory", strings are somewhat more "baked" than preons are), but there's no real experimental evidence for it; we're pretty much still at the level of some guy in ancient Greece saying "yeah, dude, everything is made of atoms." Except in ancient Greek, of course.

The two subatomic particles inside the atomic nucleus are protons (with a positive charge) and neutrons (with no charge). Electrons, which have a negative charge, orbit the nucleus in electron shells.

Calcium has 20 protons and electrons. The symbol for calcium is Ca and its atomic number is 20.

Monatomic anions are formed when atoms gain one or more electrons. The number of protons in the nucleus remains the same, giving the atom a net negative charge due to having more electrons than protons.

If all the electrons in the human body were replaced with positrons, the positrons would annihilate with nearby electrons, creating gamma radiation. This would lead to immediate destruction of the body's molecular structure and result in a catastrophic event, causing severe harm or death.

The first electron shell can hold up to 2 electrons, the second shell can hold up to 8 electrons, and the third shell can hold up to 18 electrons. Therefore, a total of 28 electrons are needed to fill the first three electron shells.

among these Electron has the least mass....

Electron dot diagrams show the arrangement of valence electrons around an atom. They are helpful in understanding chemical bonding, as they illustrate how atoms share or transfer electrons to achieve a full valence shell. By using electron dot diagrams, we can predict the types of bonds that atoms will form with each other.

They are negatively charged particles. electrons are found inside an atom, outside its nucleus.

You should understand that while neutral atoms have the same number of protons and electrons, they do not usually have the same number of protons and valance electrons, because except for hydrogen and helium, atoms also have electrons in the inner shells, which are not valance electrons. Therefore, there is no atom which has 7 protons and 7 valance electrons, although there is an element that has 7 protons, and there are several elements that have 7 valence electrons.

Energy

A neutron is still of neutral charge (no charge).

Antimatter can be thought of as protons having a negative charge and electrons having a positive charge.

If matter and anti-matter collide they annihilate one another, but neutrons remain.

The three subatomic particles are the proton, the neutron, and the electron. Protons and neutrons are located inside the nucleus. Electrons are located outside of the nucleus in the electron cloud.

Nitrogen atoms gain 3 electrons and form the nitride ion, N3-. Nitrogen atoms also form covalent bonds where they share 3 electrons and do not become ions. Bromine atoms gain 1 electron and form the bromide ion, Br-. Bromine atoms also form covalent bonds when they share 1 electron and do not become ions.

Neutrons are neutrally charged. It is not possible to determine the charge of an atom through knowledge of the number of neutrons contained within its nucleus.

Consider hydrogen, for example. It has no neutrons, one proton, and one electron. Its charge is neutral. Deuterium is hydrogen with a neutron, but also has the same charge. Tritium is hydrogen with two neutrons within its nucleus--again, no charge.

the average amount of neutrons in chlorine is 18, but there could be more or less with the different isotopes

Nitrogen has 7 electrons

The protons and the neutrons are located in the nucleus of an atom.

The electron configuration for the +2 cation of cobalt (Co) is [Ar] 3d7. This is because cobalt has an atomic number of 27, which means its neutral configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d7. When it forms a +2 cation, it loses two electrons from its 4s subshell, resulting in the configuration [Ar] 3d7.