What is an atomic nucleus?

a.)the outer part of an atom in which electrons move
b.)the outer part of an atom in which neutrons move
c.)the central part of an atom, composed of protons and neutrons
d.)the central part of an atom, composed of protons and electrons

The correct option is (C).

Explanation:

An atom is a smallest unit of the matter. Atom consists of electrons, protons, nucleus and neutrons.

Nucleus is the central part of the atom where the whole mass of the atom is supposed to be concentrated.

The electrons revolve around the nucleus. They are negatively charged particle.

The protons are located in the nucleus. They are positively charged particle.

The neutrons are located in the nucleus. They are neutral charged particle.

Therefore, an atom nucleus is the central part of an atom, composed of protons and neutrons.

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

the part of the wave he is travelling on is the crest