Chapter 3 Atoms and the Periodic Table What are atoms? Tiny units that determine the properties of all matter What does atom mean in Greek? Unable to be divided

What is the atomic mass? The mass of an atom based on the average mass of isotopes of the element The mass of the protons + the neutrons in the nucleus of the element example 6 C 12 has an atomic mass of 12

What is the atomic number of an atom? The number of protons in the nucleus The number of protons gives the atom its identity 6 C 12 Has 6 protons

The central portion of an atom, containing both neutrons and protons What is a nucleus? The central portion of an atom, containing both neutrons and protons

What is a neutron and where is it located? The neutral particle found in the nucleus of an atom which has a mass about equal to a proton Determined by subtracting the number of protons from the mass number of the element Example: 8 O 16 neutrons= 16-8 =8

Positively charged particle in the nucleus of an atom What is a proton? Positively charged particle in the nucleus of an atom Atomic number of an element gives an element its identity Example 7 N 14 has 7 protons

What is an electron and where is it located The negatively charged particle in the electron cloud of an atom Equal to the atomic number of a neutral element and the atomic number minus the charge for an elemental ion Example: 6 6 C C+4 12 has 6 12 has 6-4=2

What are valence electrons? outer most energy level electrons

Information represented for an element 8 atomic number (protons) O element symbol 15.99 atomic mass

What is electron affinity? The attraction of an atom for an additional electron Metals have low affinity because they give away electrons Nonmetals have high affinity because they take on electrons The electron affinity tends to increase from left to right in the periodic table and from bottom to top

What are families/groups? Elements grouped together by common properties. They fall in the same vertical column of the periodic table Column #1alkali metals (+1 oxidation #) Column #2 alkaline earth metals(+2 oxid #) Column #3-12 transition metals (many have multiple oxidation number-least reactive of the metals) Column #16 chalcogens (-2 oxidation #) Column #17 halogens (-1 oxidation #) most reactive nonmetals Column #18 noble gases (0 oxidation #) nonreactive due to filled outer energy level lanthanide series actinide series

Where is the period in the periodic table? Horizontal rows in the periodic table Each represents an energy level

What are metals? Groups of elements that has: Luster (shiny) Good conductors of heat and electricity 1-3 valence electrons Located in the periodic table left of the metalloids excluding H Solids are room temperature(ex mercury)

Elements that have properties of both metals and nonmetals. What are metalloids? Elements that have properties of both metals and nonmetals. Located diagonally between the metals, nonmetals B, Si, Ge, As, Sb, Te, At

What are nonmetals? Elements that do not have properties of metals Located on the right side of the periodic table Have more than 4 valence electrons Dull/lack luster Do not conduct heat or electricity well Typically gases or brittle solids at room temperature

What is a subscript? Small lowered number after the symbol for an element that indicates the number of atoms of the element present in the formula of the molecule Subscripts of one in a symbol are understood and therefore not shown Example O2 or NaCl or K2SO4

What is ionization energy Energy needed to remove an electron from an atom. Ionization energy tends to increase from left to right and decrease from top to bottom

Periodic trends of Elements Reactivity of metals increases down the periodic table and from right to left across the periodic table Reactivity of non metals increases up the periodic table and from left to right across the periodic table Atomic radius increases down the periodic table and form right to left across the periodic table