A Walk through the Elements

Atoms Means “cannot be divided” All matter is made up of “elements” An element is matter that is made up of atoms of only one kind. Ex: iron is made up of only iron atoms

Composition of atoms Atoms are made up of protons (+ charge), neutrons (neutral charge) and electrons (-charge) Protons and neutrons are in the nucleus of the atom Electrons occupy the space surrounding the nucleus.

Atomic Number The number of electrons in a neutral atom equal the number of protons in the atom This is the Atomic Number of the element It is the number of electrons OR protons

Electron Cloud Neil Bohr calculated the exact energy levels that electrons travel However, new theory states the electrons travel in a region surrounding the nucleus which is called the electron cloud. They could be anywhere!

Role of Neutrons An atom of a particular element has a specific number of protons. But a particular atom may have varying number of neutrons in the nucleus.

Isotopes Most carbon atoms have 6 protons and 6 neutrons. However, some carbon atoms have 7 or 8 They are all carbon atoms because they all have 6 protons. These three types of carbons are called isotopes. (Fig:15, p41)

Mass Number Is the number of protons and neutrons When atoms have the same number of protons and neutrons, they are relatively stable. Carbon-12 is the most stable isotope of Carbon. Some are unstable because they have a different # of protons and neutrons

Radioactive Decay When these particles become unstable they release energy and particles This release of nuclear particles and energy is called radioactive decay. If it releases a proton, a new element is formed. (see p 43)

The Periodic Table A period is a row of elements that change gradually and predictable. A group (or family) contains elements that have similar chemical and physical properties.

Transititon Elements Groups 3-12 All metals Contains inner transition metals placed below the main tables These are called Lanthanides, and Actinides series.

Metals Most abundant element Except for mercury, all metals are solids High melting points Has luster, is a good conductor of heat and electricity, malleable and ductile

Nonmetals Nonmetals are gases or brittle solids at room temp. Poor conductors of heat and light Only 17 nonmetals, but many are essential to like – carbon, sulfur, nitrogen oxygen, phosphorus, iodine

Metalloids The elements between metals and nonmetals It shares some properties with metals and some properties with nonmetals Include boron, silicon, germanium, arsenic, antimony, tellurium, polonium, astatine

Alkali Metals Group 1 – active metals Silver, solid, low density and low melting point NaCl is table salt Na and K are also found in potatoes and bananas

Alkaline Earth Metals Group 2 denser, harder, have a higher melting point Active but not as active as the alkali metals

Group 13 Boron The Boron Family All metals except Boron (a brittle black, metalloid) Bororn – used for cookware Aluminum – Used for soda cans, cookware, siding for homes. And baseball bats Galium – used for making computer chips

Group 14 - Carbon C is a nonmetal, Si and Ge are metalloids, tin and lead are metals All living things are composed of Carbon Most abundant is Si. Found in sand, used to make glass and semiconductors

Group 15 Nitrogen

Group 16 Oxygen

Group 17 Halogens

Group 18 Nobel gases