Presentation on theme: "Atoms w What are atoms? w What’s in them? w Why are they important? w Can you combine them?"— Presentation transcript:
Atoms w What are atoms? w What’s in them? w Why are they important? w Can you combine them?
What is an atom? w An atom is the smallest particle of matter w An atom consists of a nucleus surrounded by one or more electrons.
Atoms are made of smaller particles w Protons w Neutrons w Electrons w Quarks w Leptons
The Nucleus w The nucleus is where the protons and neutrons are located. w It accounts for 99.9% of the mass.
What is the charge of each particle? w Protons are positive w Neutrons are neutral w Electrons are negative
Quarks w Quarks make up protons and neutrons. w Six different quarks w Three quarks make up a proton. w Three quarks make up a neutron.
Where are the electrons? They orbit around the nucleus and can be lost, gained, or shared with another atom.
Electron Cloud w Space where the electrons are likely to be found.
Energy Levels w Electrons are arranged in energy levels. w Electrons with the lowest energy can be found in the energy level closest to the nucleus. w Energy levels can hold 2, 8, 18
How are electrons arranged… w For eighth grade curriculum you only need to teach the first three energy levels.
Valence Electrons w The electrons in an atom are not all the same distance from the nucleus. Those farthest away from the nucleus are called valence electrons. w Valence electrons are involved in chemical bonds.
Electron Dot Diagram w Used to represent the valence electrons of an atom. w Elements can have between 1-8 valence electrons. w During a chemical bond the element usually ends up with either 0 or 8 valence electrons.
Chemical Bonds w Forms between two atoms when valence electrons move between them. The valence electrons may be transferred from one atom to another, or they may be shared.
Atoms w Must have an equal number of protons and electrons. w The overall charge of an atom is neutral. w The number of neutrons can change. Atoms of the same element with a different number of neutrons are called isotopes.
Atomic Number w The atomic number is the number of protons in the nucleus of an element. w The atomic number identifies the element.
Mass Number w The mass number of an atom is the sum of the protons and the neutrons in its nucleus. w Mass Number = # protons + # neutrons Atomic Number Atomic Mass
w The unit of measurement for the small mass of an atom is an amu (atomic mass unit). The mass of a proton or neutron is equal to one amu.