A Walk through the Elements

http://www.chemsoc.org/viselements/Pages/pdf/intro_patterns.PDF

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