Chemistry
November 19
Atom

The smallest part of an element that possesses all properties of
that element.
The Structure of the Atom

The current model of the atom includes a tiny nucleus with
negatively charged particles in electron clouds around the
nucleus.
Atom
Nucleus


The central core of an atom made up of protons and neutrons.
The nucleus has most of the mass of the atom and it has a positive
charge (+)
Proton

A positively-charged particle in the nucleus of an atom.
Neutron

A particle in the nucleus of an atom which has no electrical charge.
electron


A rapidly-moving, negatively-charged particle in an atom
The electron is very small compared to the proton and neutron
Electron Cloud

The cloud of negative electric charges (electrons) that surround the
nucleus of an atom.
The Size of the Atom

To understand the relative size of the parts of an atom, imagine BC
Place or any large football stadium. The nucleus would be a small
marble in the centre of the field. The electrons would be like
mosquitoes buzzing around in the seats.
The Size of the Atom

But…… atoms are very small. The period at the end of this
sentence could hold
1 000 000 000 000 000 000 atoms.
Atomic Number

The number of protons in the nucleus of an atom of an element.
For example, the element hydrogen has an atomic number of 1. All
atoms of hydrogen have one proton, and any atom that has just
one proton is a hydrogen atom.
Atomic Mass Number


It is the total number of protons and neutrons in an atom of the
element.
It represents the mass of an element.
Isotopes



Atoms of the same element with different numbers of neutrons..
All atoms of the same element have the same number of protons,
but they may have different mass numbers. This happens because
they have different number of neutrons.
For example: there are 3 isotopes of hydrogen in nature:
hydrogen-1, hydrogen-2, and hydrogen-3. They all have one
proton, but their mass number is 1, 2 and 3.