The Atom Unit 2 Topic 1 Subatomic Particles

The Atom Unit 2 Topic 1

Subatomic Particles l The smallest particle of an element that still has the properties of that element is the atom. l Atoms are made up of subatomic particles called Protons, Neutrons, and Electrons. l Atoms of the same element have the same number of protons and atoms of different elements have a different number of protons.

Protons continued l Therefore we use the number of protons to identify an element and call this the atomic number of the element. l The subatomic particles differ in their mass, charge, and relative position within the atom.

Charge, Mass & Location Particle Charge Mass Location Proton +1 1 amu Nucleus Neutron 0 1 amu Nucleus Electron -1 0 amu Outside the nucleus

Protons, Neutrons & Electrons # Protons If neutral then also # electrons Atomic Weight (Mass) = Weighted average of all known isotope Mass Number = Mass of specific atom (Protons+Neutrons) Carbon-12 OR ___ protons ___ neutrons 12 C Carbon-13 OR ___ protons ___ neutrons 13 C

Shape l An atom is basically spherical in shape with a dense positively charged nucleus containing the protons and neutrons l The nucleus is surrounded by electron clouds, which are at specific distances from the nucleus.

Represent! l When you draw a representation of an atom, you must draw each particle in their correct positions l For neutral atoms (atoms which have no net charge), the number of protons must equal the number of electrons.

Neutrality l When the number of protons equals the number of electrons, then the number of positive particles in the atom equals the number of negative particles in the atom. This results in the atom itself having no net charge (being neutral).

Lithium - 7 l Ex: Li (atomic # 3) l # of protons = 3 l # of neutrons = 7 - 3 = 4 l # of electrons = 3 l charge = (+3 – 3) = 0

Nitrogen - 15 l Ex: C (atomic # 6) l # of protons = 7 l # of neutrons = 12 - 6 = 8 l # of electrons = 7 l charge = (+7 – 7) = 0

Neon - 20 l Ex: Ne (atomic # 10) l # of protons = 10 l # of neutrons = 20 - 10 = 10 l # of electrons = 10 l charge = (+10 – 10) = 0

9 Be 8 Be+2 30 P 31 P-3