The Role of Protons and Electrons in Atoms- Year 9

Atoms

The building blocks of matter, made of protons, neutrons, and electrons.

Protons

Positively charged particles in the nucleus. Determine the element and the atomic number.

Neutrons

Neutral particles in the nucleus. Add mass but don't affect charge.

Electrons

Negatively charged particles orbiting the nucleus. Balance the protons to make an atom neutral.

Atomic Number

The atomic number of an element is the number of protons in the nucleus.

Key Point

The number of protons uniquely defines an element. If you change the number of protons, you change the element. Each element has a unique atomic number.

Neutral Atoms

When an atom has the same number of protons and electrons, it is electrically neutral.

Charge Calculation

Protons have a +1 charge. Electrons have a -1 charge. If there are equal numbers of protons and electrons, the positive and negative charges cancel out, resulting in no overall charge.

Example of Neutral Atom

A carbon atom has 6 protons and 6 electrons, making it neutral.

Positively Charged Ion

If an atom loses electrons, it becomes positively charged (+ion).

Negatively Charged Ion

If it gains electrons, it becomes negatively charged (-ion).

Role of Electrons

Electrons: Negatively charged particles orbiting the nucleus.

Equal Numbers in Neutral Atoms

In a neutral atom, the number of electrons equals the number of protons.

Ion Formation

If the atom gains or loses electrons, it becomes charged (an ion).