Ch 3 Atoms and Periodic Table Notes Vocab: nucleus, proton, neutron, electron, Energy level, orbital, Valence electron, Periodic law, Period, Group, Ionization, Ion, Cation, Anion, Atomic number, Atomic mass number, Isotopes, Atomic mass unit, Average atomic mass, Metals, Nonmetals, Semiconductors, Alkali metals, Alkaline-earth metals, Transition metals, Halogens, Noble gases

3.1 Atomic Structure What gives different matter distinct properties? - the atoms in that type of matter Atoms are tiny units that determine properties of matter - each element has its own atom

Dalton’s Atomic Theory – 1808 English schoolteacher Every element is made of tiny particles called atoms that can’t be divided. Atoms of the same element are exactly alike. Atoms of different elements can join to form molecules. - We have since learned that atoms can be divided.

Atomic Structure Nucleus = center of atom Protons + neutrons Overall positive charge

Electron Cloud = surrounds nucleus Contains space where electrons are found Overall negative charge Overall positive and negative attraction keeps electron cloud close to the Nucleus

Sub-Atomic Particles Proton = “+” charged molecule in nucleus Written as “p+” Mass of 1.67 x Neutron = a neutral particle in nucleus (NO charge) Written as “n” Mass of 1.67 x

Electron = a “-“ charged particle moving around the outside of nucleus in an electron cloud… think of fan blades Written as “e-“ Mass of 9.11 x …. Very little mass Atoms have no overall charge because they have an equal number of protons and electrons.

Electron Cloud Orbitals It is impossible to know the exact location of a given electron in its electron cloud. So… we have a general area based on an electron’s energy level. General rule = the more energy an electron has, the farther from the nucleus and the positive protons it can get.

Orbitals = a region in an atom where there is a high probability of finding electrons; we only look at two types, there are more. S-orbitals are spherically shaped –Holds first two electrons of every element –Is the lowest energy level –After 1st S-orbital is full, a second fills with 2 more e-

P-orbitals are peanut shaped –When the 2 s-orbitals are full (4e-), the 5th through 10th electrons will fill p-orbitals –These electrons have slightly more energy than the first 4

Electron Clouds and Energy Electrons move about the electron clouds (orbitals) based on their energy levels. Analogy: sun and planets

General Atomic Model 1st energy level –s-orbital with 2e- 2nd energy level –s-orbital with 2e- –3 p-orbitals with 2e- each = 6e-

Valence electron = an electron in the outermost energy level of an atom hydrogen has 1; helium has 2; lithium has 1 these are the electrons that will allow the atom to react with others

3-2 A Guided Tour of the Periodic Table The periodic table is a visual representation of the elements organized by properties. Each element has a symbol Organized by # of protons; also called the atomic number

Periodic law = properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number, or number of protons in their atoms.

History of the periodic table Dmitri Mendeleev ( ) Organized 70 known elements into a able according to common characteristics. Problem  there were many empty spaces and it was very long

Henry Moseley ( ) Determined the atomic number of elements and recognized Mendeleev’s table to what we know today

The Periodic Table Periods are horizontal rows There are 7 periods The # protons and electrons increases from left to right Other properties also follow pattern including size of molecule

Groups are vertical columns Also called families because elements in the same group share physical and chemical properties. Elements in a group have the same # of valence electrons Each group is identified by a number and letter

Ions Atoms that do not have a filled outermost energy level may undergo a process called ionization. The atom will either gain or lose valence electrons. Example: Element Lithium from Group 1 is very reactive. Li will give away its 3rd electron and become a positive ion.

All elements in the first group on the periodic table will react the same way A positive ion is called a cation A negative ion is called an anion

Each element and its information can be found in a box on the periodic table. General format:

Atomic number Is equal to the number of protons in the nucleus Will also equal the number of electrons in the electron cloud Will always be a whole number on the table (no decimals)

Atomic mass The mass of the nucleus of the atom The combined number of protons AND neutrons in an atom Atomic mass = p + n Will always be the larger number

Protons = Electrons = Neutrons = Protons = Electrons = Neutrons = 8 Oxygen Carbon 6

Protons = Electrons = Neutrons = Protons = Electrons = Neutrons = 4 Helium 2 5 Boron 11

Isotopes Different versions of an element that have different numbers of neutrons. They have the same # protons, but different masses

This is why the average atomic masses on the periodic tables are decimals, the mass is a combination of all isotopes. –Ex: Hydrogen has 1p+, 1e-, and has a mass of because it is mostly found as an isotope with no neutron

The mass of an atom It is very small, so they decided to measure a Carbon-12 atom (6 protons and 6 neutrons) and divide into 12… meaning they said each proton and neutron equals 1 atomic mass unit

3-3 Families of Elements - How are elements classified? Metals versus Nonmetals Most elements are metals –Most metals are shiny solids that can be stretched and shaped –They are good conductors of heat and electricity

Nonmetals are usually on the right of the periodic table –Include solids, liquids and gases –Nonmetal solids are usually poor conductors of heat and electricity –Some can conduct under certain conditions – semiconductors

Metals – There are 4 different groups The Periodic Table

Alkali Metals - Group 1 (except hydrogen) Soft and shiny Have one valence electron; forms cations very easily React violently with water; elements are usually stored in oil Only found in compounds in nature video

Alkaline Earth Metals – Group 2 Have 2 valence electrons May react to form ions with +2 charge Calcium is very important in skeletons Magnesium is the lightest structural material

Transition Metals – Groups 3-12 May lose electrons to form multiple cations All conduct heat and electricity –Copper wire Can be stretched and shaped without breaking; gold and silver jewelry

Synthetic Elements Some of the transition metals are man- made – Tc-43, Pm-61 and Atomic numbers 93 and above Many are radioactive… the nuclei are continually decaying to produce different elements

Nonmetals – all but Hydrogen are found on the right of P. Table Carbon is a very important non-metal Pure state – graphite, pencil lead Diamond In body structure

Halogens – Group 17 Very reactive; gain electron to form -1 anions Chlorine is used to kill bacteria – pools, drinking water Fluorine anion prevents tooth decay

Nobel Gases – Group 18 Exist as single atoms because they are inert or unreactive… the outer energy level is full of electrons Neon is used in “neon” signs Helium is less dense than air… it floats

Semiconductors or metalloids – 6 elements Have some properties of metals Under certain conditions, they can conduct heat and electricity Silicon is very important in modern technology