Chemistry 103 Lecture 4

Outline I. Matter Classified (CH3) II. The Periodic Table (CH4) - The “Atom” defined - History - Atomic Symbols - Atomic Mass

Density in Review What mass of gold (density = 19.3g/cm 3 ) occupies the same volume as 80.0g of lithium (density = 0.534g/cm 3 )?

Chemical vs Physical??? Popping a balloon Burning a marshmellow Snapping a twig Water evaporating from a lake Metabolizing a meal Frying an egg

Matter Pure SubstanceMixture Element Compound

Pure Substances: Compounds Compounds –A chemical combination of 2 or more elements. –A pure substance that can be broken down into simpler substances by chemical means. Salt (NaCl) Table sugar (C 12 H 22 O 11 ) Water (H 2 O) NOTE: CO is different from Co

Elements in a Compound “Table salt” is a compound that contains the elements sodium and chlorine. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Pure Substances Elements and Compounds Elements and compounds have definite compositions, and each has a set of properties that are unique. Which formulas represent elements (A) and which represent compounds (B)? –C(A) –CO 2 (B) –NH 3 (B) –C 60 (A)

Matter Pure SubstanceMixture Element Compound

MATTER Mixtures: a physical combination of two or more pure substances in which each substance retains its own chemical identity

Mixtures A mixture is a type of matter that consists of: Two or more substances that are physically mixed, not chemically combined Two or more substances in different proportions Substances that can be separated by physical methods Example: Pasta and water can be separated with a strainer.

Matter Pure Substance Mixture Element Compound Heterogeneous Homogeneous

Mixtures Homogeneous Mixtures (solutions) –The composition is uniform throughout –The different parts of the mixture are not visible –air, salt water, alloys (i.e. brass, bronze) Heterogeneous Mixtures –The composition of substances is not uniform –The composition varies from one part of the mixture to another –The different parts of the mixture are visible –potting soil, oil and water

Classification of Matter

Elements v. Compounds v. Mixtures Identify each of the following as an element(A), compound(B), homogeneous mixture(C), or heterogeneous mixture(D). carbon monoxide (CO) oxygen (O 2 ) salt mixed with sugar salt mixed with water oil and water

A closer look at Elements & The Periodic Table

Modern Periodic Table Mendeleev – Father of the Periodic Table Periodic Law of the Elements – when elements are arranged in a particular order (increasing atomic number), elements of similar properties occur at periodic intervals Arranged into: –Groups/families – vertical columns –Periods – horizontal rows

Arrangement of the Periodic Table The blocks of the periodic table:

The Periodic Table – All Stretched Out

Names of Some Representative Elements Several groups of representative elements are known by common names. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Organization of the Periodic Table Metals –Have luster, are malleable, conduct electricity Nonmetals –Do not have the properties of metals Metalloids –Have some metallic properties and some nonmetallic properties

A closer look still

The Conjecture of Atoms As early as 500 B.C., Greek Philosophers proposed that all matter is made up of atoms –Atom: The smallest individual particle of an element that maintains the properties of that element Atomos - indivisible

Dalton’s Law of Atomic Theory 1.All matter is composed of extremely small particles called atoms. 2.Atoms of a given element are identical in their physical and chemical properties. 3.Atoms of different elements differ in their physical and chemical properties.

Dalton’s Law of Atomic Theory 4. Atoms of different elements combine in simple, whole- number ratios to form compounds. 5. In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed.

Atom Defined An atom is the smallest particle of an element that can exist and still have the properties of the element. The fundamental building block of matter.

Subatomic Particles Today, we know that atoms are made up of smaller, more fundamental particles called subatomic particles. Protons, Electrons & Neutrons

Electron Discovered J.J. Thomson Proposed the “Raisin Muffin” model of the atom. e- e- e-

Rutherford’s Gold-Foil Experiment Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Structure of the Atom An atom consists Of a nucleus that contains protons and neutrons Of electrons in a large empty space around the nucleus Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

Structure of the Atom An atom is composed of a nucleus and an area called the electron cloud –The nucleus is very small compared to the size of the atom –The nucleus contains the protons and the neutrons –The electrons are constantly moving around in the electron cloud –In a neutral atom, the number of electrons is equal to the number of protons

Atoms: Composed of 3 Subatomic Particles SymbolRelative Charge Mass Proton p or p x g Neutron n or n o x g Electron e x g

The Atom The nucleus of an atom carried most of the mass. A matchbox full of material of such density would weigh 2.5 billion tons

The Atom If an atom were scaled upwards in size so that the nuclei was 2 cm in diameter, the atom would have a diameter twice the length of a football field

Atomic Symbols X QA Z Mass number = number of protons + number of neutrons Atomic number = number of protons Defines the element Charge = Number of protons - number of electrons

The atomic number Is specific for each element Is the same for all atoms of an element Is equal to the number of protons in an atom Appears above the symbol of an element Atomic Number 11 Na Atomic Number Symbol

State the number of protons in each: 1. A nitrogen atom A) 5 protons B) 7 protons C) 14 protons 2. A sulfur atom A) 32 protons B) 16 protons C) 6 protons 3. A barium atom A) 137 protons B) 81 protons C) 56 protons Learning Check

Variability in the Number of Electrons and Neutrons Isotopes –Atoms of the same element (same number of protons) with different numbers of neutrons Ions –Charged particles that have either lost or gained electrons –These have the same number of protons and neutrons, but a number of electrons that differs from the number of protons

Atomic Symbols X QA Z Mass number = number of protons + number of neutrons Atomic number = number of protons Charge = number of protons – number of electrons

An atom has 14 protons and 20 neutrons. 1. Its atomic number is A) 14B) 16C) Its mass number is A) 14B) 16C) The element is A) SiB) CaC) Se Learning Check

Atomic Symbols X QA Z Mass number = number of protons + number of neutrons Atomic number = number of protons Charge = number of protons – number of electrons

Using Atomic Symbols to Calculate Numbers of Subatomic Particles How many electrons, neutrons, and protons are in the following particles? # protons#electrons#neutrons 40 Ca 40 Ca C 12 C

43 Write the nuclear symbols for atoms with the following subatomic particles: A. 8 p +, 8 n, 8 e - ___________ B. 17p +, 20n, 18e - ___________ Learning Check