Atoms and orbitals

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

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

Wikipedia

• Atomic orbital
• Molecular orbital
• Electron configuration
• Electron orbital
• Atom