Atoms

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#19.

Topic: Atoms

IAN #17

Atom: The smallest

particle of an element

Structure of an Atom

Protons

Small positively charged

particle in the nucleus of an

atom.

Neutrons

Particles with no charge

Electron

Tiny, negatively charged, high energy particle that moves in the space outside the nucleus of an atom called the electron cloud or orbit.

Atomic Number The number of protons in the nucleus of

an atom. This determines what the element

is.

In a stable atom (no charge), there must be

an equal numbers of protons and

electrons.

For example, the atomic number of

oxygen is 8, so there are 8 protons and 8

electrons in an oxygen atom.

Example: Oxygen Atom

Carbon Atom

If the atomic number of carbon is 6, how

many protons and electrons does it have?

Atomic Mass

The average mass of one atom of an

element.

Mass # (rounded to nearest whole number)

= (# of Protons) + (# of Neutrons)

If a sulfur atom has an atomic mass of

about 32 and there are 16 protons, how

many neutrons will it have?

CCarbon

6 12.011Atomic number

Atomic Mass

Symbol

Element

Atoms and Periodic Table