Properties of Atoms and the Periodic Table Chapter 18.
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Transcript of Properties of Atoms and the Periodic Table Chapter 18.
Properties of Atoms and the Periodic Table
Chapter 18
18-1: Structure of the Atom
Atoms
Atom – the smallest unit of matter that can’t be broken down by chemical means
Atoms are made up of three types of particles: Proton: (+) charged Neutron: no charge Electron: (-) charged
Nucleus – consists of protons and neutrons
Atoms
A proton is about 1000 times larger than an electron
Electron cloud – the region where electrons orbit the nucleus
18-2: Masses of Atoms
Atomic Mass
Atomic mass = protons + neutrons
Atomic number - The number of protons in the nucleus of an atom, which determines its place in the periodic table
Atomic Mass
Atomic Facts Atomic number = protons = electrons
Atomic mass
- Atomic number # of neutrons
Maximum number of electrons 1st energy level – 2 electrons 2nd energy level – 8 electrons 3rd energy level – 18 electrons
Atomic Mass
Element – A substance made up a group of similar atoms that have the same number of protons
Atomic Mass
Isotopes – Atoms of an element that have different numbers of neutrons
Chemical Bonds
Valence electron – An electron that is found in the outermost shell of an atom Lewis dot diagrams can be used to show the
transfer of valence electrons
Chemical Bonds
Chemical bonds form between groups of atoms because most atoms become stable when they have eight electrons in the valence shell (Octet rule)
Chemical Bonds
Compound – A substance made of the bonded atoms of two or more different elements
Chemical Bonds
Ion – an atom or group of atoms that has an electric charge because it has gained or lost electrons Ionic bond – the attractive force between
oppositely charged ions
Chemical Bonds
Covalent bond – chemical bond that shares electrons
Molecule – A group of atoms held together by covalent bonds
Chemical Bonds
Hydrogen bond - A chemical bond in which a hydrogen atom of one molecule is attracted to an electronegative atom
Chemical Bonds
Polarity
Polar – molecules with partial charges on opposite ends
Water is the most abundant compound in organisms
Average Atomic Mass
Average atomic mass is not a straight average but a weighted average based upon the percent isotopic ratio of the element.
(Mass1 x % Isotope1) + (Mass2 x % Isotope2) + (etc.)
100 100
Average Atomic Mass
43.00% of 74.2 amu; 57.00% of 77.1 amu (Mass1 x % Isotope1) + (Mass2 x % Isotope2) + (etc.)
100 100 (74.2 amu x 43.00) + (77.1 amu x 57.00)
100 100 (3190.6 amu) + (4394.7 amu)
100 100 31.906 amu + 43.947 amu 75.853 amu
18-3: The Periodic Table
The Periodic Law
The modern periodic table is based on atomic number, or number of protons.
The Periodic Law
Period – Each row in the table of elements Hydrogen, the first element in Period 1, has one
electron in its first energy level. Lithium, the first element in Period 2, has one
electron in its second energy level.
The Periodic Law
Group – Each column in the periodic table The elements in a group have similar electron
configurations
The Periodic Law
Classes of Elements
Metals – elements that are good conductors of electric current and heat Except for mercury, metals are solids at room
temperature
Classes of Elements
Metals (cont.) Malleable – able to be hammered or pressed
permanently out of shape without breaking or cracking
Ductile – can be drawn into thin wires
Classes of Elements
Transition metals – elements that form a bridge between the elements on the left and right sides of the table Many of their compounds are colored
Classes of Elements
Nonmetals – elements that are poor conductors of heat and electric current Many nonmetals are gases at room temperature Nonmetals that are solids at room temperature
tend to be brittle Brittle – hard but liable to break or shatter easily
Classes of Elements
Metalloids – elements with properties that fall between those of metals and nonmetals
18-3: Representative Groups
Representative Groups
Elements in a group have similar properties because they have the same number of valence electrons
Representative Groups
Alkali metals – (Group 1A) These metals have a single valence electron and are extremely reactive
Representative Groups
Alkaline earth metals (Group 2A) – have two valence electrons
Representative Groups
Boron family (Group 3A) – have three valence electrons
Representative Groups
Carbon family (Group 4A) – have four valence electrons Clay used to
produce this
pottery contains
silicon
Representative Groups
Nitrogen family (Group 5A) – have five valence electrons
The numbers on the bags of fertilizer are, from left to right, the relative amounts of nitrogen, phosphorus, and potassium.
Representative Groups
Oxygen family
(Chalcogen) –
(Group 6A) have six
valence electrons
Representative Groups
Halogens (Group 7A) – have seven valence electrons
Representative Groups
Noble gases (Group 8A) – Helium has two valence electrons. Each of the other noble gases has eight valence electrons.
Noble gases are extremely
unreactive