The Nature of Matter Chapter 2.1

Atoms: the building blocks of elements Atom – smallest particle of an element that has the characteristics of that element Structure effects their properties and chemical behavior

Atoms and their interactions Element – a substance that can’t be broken down into simpler substances

Nucleus – center of the atom Protons – positive charge Neutrons – neutral charge Electrons – around nucleus w/ negative charge

The structure of an atom

Electron Energy Levels 1st – can hold 2 electrons 2nd – can hold 8 electrons 3rd – can hold 18 electrons

An element is a pure substance consisting of only 1 type of atom Elements and Isotopes An element is a pure substance consisting of only 1 type of atom

Natural Elements in living things Major elements in the human body: C, H, O, N Make up more than 96% of the mass of the human body

Vital role in maintaining healthy cells Trace Elements Trace: Ca, P, K, S, Na, Cl, Mg, Fe, Zn, Cu, I, Mn, B, Cr, Mo, Co, Se, F Vital role in maintaining healthy cells

Isotopes Atoms that have the same # of protons, but a different # of neutrons Named by # of protons & neutrons Carbon-12 vs carbon-14

Isotopes are useful to scientists Some nuclei of isotopes are unstable and break apart Give off radiation Can be used in medicine to diagnose or treat some diseases

2 or more different atoms chemically combined in a specific ratio Chemical Compounds 2 or more different atoms chemically combined in a specific ratio Bonding – determined by electrons

Ionic bonds – electrons are gained or lost by individual atoms atoms transfer electrons to form a bond creates ions Salt is an example

Atoms that gain or lose electrons have an electrical charge Ions Atoms that gain or lose electrons have an electrical charge An ion is a charged particle made of atoms

Covalent bonds – electrons are shared – creates a molecule

A group of atoms held together by covalent bonds Molecules A group of atoms held together by covalent bonds Water is an example

Van der Waals Forces Intermolecular forces of attraction due to opposite charged regions on nearby molecules Gecko’s foot/wall