Atoms and orbitals

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Subject classification: this is a chemistry resource.

We'll start with some definitions:

atom
a particle that is indivisible during chemical reactions
element
atoms of the same atomic number

An atom = nucleus (positive charge) + electrons (negative charge)

Atomic number = number of protons in the nucleus = number of electrons (atoms are neutral - they have no overall charge)

electrons
have an electric charge of -1.6022 x 10-19 Coulomb and a mass of 9.11 x 10-31 kg
proton
nuclear particle with a positive charge equal to that of an electron (+1.6022 x 10-19 Coulomb) and a mass of 1.6726 x 10-27 kg
neutron
particle in the nucleus, has about the same mass as a proton but no charge
mass number
total number of protons and neutrons in the nucleus
nuclide
particular nucleus characterized by atomic number (subscript) and mass number (superscript), e.g. 12C6 is an isotope of carbon with 6 protons and 6 neutrons in the nucleus
isotope
atoms with the same atomic number but different mass numbers (same number of protons, same number of electrons but different number of neutrons)

quiz[edit | edit source]

1 An ________ is a particle that is indivisible during chemical reactions.

atom
element
electron
proton

2 Atoms of the same atomic number are called ________.

atom
element
electron
proton

3 An atom consists of a ________ with a positive charge and ________ with a negative charge.

nucleus | electrons
electrons | nucleus
proton | neutron
neutron | proton

4 The atomic number is equal to the number of ________ in the nucleus and the number of ________.

protons | electrons
electrons | protons
neutrons | electrons
electrons | neutrons

5 A ________ is a nuclear particle with a positive charge equal to that of an electron.

electron
proton
neutron
atom

6 A ________ is a particle in the nucleus with about the same mass as a proton but no charge.

electron
proton
neutron
atom

7 The mass number is the total number of ________ and ________ in the nucleus.

protons | neutrons
electrons | protons
electrons | neutrons
protons | electrons

8 A ________ is an isotope of carbon with 6 protons and 6 neutrons in the nucleus.

element
electron
proton
12C6

9 An ________ consists of atoms with the same atomic number but different mass numbers.

element
electron
isotope
nuclide


Readings[edit | edit source]

Wikipedia[edit | edit source]