Properties of Atoms and the Periodic Table

Atoms Unit of all matter, building blocks of elements Smallest piece of matter that has the properties of the element Make up elements, which combine to make up compounds

Elements Elements are abbreviated in scientific shorthand – first letter or two of element’s name

Latin Names Element Symbol Latin name Copper Cu cuprum Gold Au aurum Lead Pb plumbum Mercury Hg hydrargyrum Potassium K kalium Silver Ag argentum Sodium Na natrium Tin Sn stannum

Organic Element Trace Metal

Example

Compounds Def: two or more elements combined, pure substance.

Example

Example 2

Example 3

Structure of the Atom Nucleus: Protons Neutrons Electrons

Atomic Structure

Protons Much larger and heavier than electrons Protons have a positive charge (+) Located in the nucleus of the atom 

Neutrons Large and heavy like protons Neutrons have no electrical charge Located in the nucleus of the atom 

Electrons Tiny, very light particles Have a negative electrical charge (-) Move around the outside of the nucleus

Subatomic Particles Particle Symbol Charge Relative Mass Electron e- 1- 0 Proton p+ + 1 Neutron n 0 1

Atomic Structure 10-13 cm 10-8 cm

Atom Models Scientist use scaled-up models to represent atoms. Early models of atoms used a solid sphere Current electron cloud model shows electrons traveling in specific energy levels around a nucleus of protons and neutrons.

Early Model

Electron Cloud Model Example 1

Electron Cloud Model: Example 2

Masses of Atoms (1) Atomic Mass (2) Isotopes (3) Ions

Atomic Mass Definition: Composed mostly of the protons and neutrons in the nucleus. Unit of measurement for atomic particles is atomic mass unit (amu), which is 1/12 the mass of a carbon atom. Atomic Number: this is also the number of protons in an atom Mass Number: The sum of the number of protons and neutrons in the nucleus of an atom

Atomic Number on the Periodic Table 11 Na Atomic Number Symbol

Proton Number identifies an Element 11 Na 11 protons Sodium

Reading Elements on the Periodic Table Mass number = number of protons + number of neutrons

Quick Check A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons

Calculating Subatomic Particles 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15 e- 30 e-

Isotopes Definition: Atoms of the same element with different numbers of neutrons

Isotopes

Isotopes Different isotopes have different properties The number of protons for a given atom never changes. The number of neutrons can change.  Two atoms with different numbers of neutrons are called isotopes

Isotopes of Chlorine 35Cl 37Cl 17 17 chlorine - 35 chlorine - 37

Quick Check Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______

Answer Key 12C 13C 14C 6 6 6 #p 6 6 6 #n 6 7 8 #e 6 6 6

Quick Check An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67

Ions An atom that carries an electrical charge is called an ion If the atom loses electrons, the atom becomes positively charged (because the number of positively charged protons will be more the number of electrons). Also called Cation If the atom gains electrons, the atom becomes negatively charged. Called Anion

Ions (continued) The number of protons does not change in an ion The number of neutrons does not change in an ions So, both the atomic number and the atomic mass remain the same.

Ion Illustration This atom has lost an electron. Now it has one more proton than electron. One more proton means one more positive charge. This makes the total charge of the atom POSITIVE. This atom has gained an electron. Now it has one less proton than electron. One less proton means one less positive charge. This makes the total charge of the atom NEGATIVE.

The Periodic Table Elements are organized to their properties in a chart called the Periodic Table. Elements are arranged in order of increasing atomic number. Periods – Horizontal Rows Groups – Vertical Columns

Groups Groups share similar properties Elements of the same group have the same number of electrons in their outermost shell (energy level). Energy Shells has a maximum number of electrons. Level 1: 2 e-. Level 2: 8 e-. Each row in the table ends when an outer energy level is filled.

Valence and Shells

Periods Horizontal rows of elements that contain increasing number of protons and electrons. Elements are classified as metals, non-metals, or metalloids. Elements are synthesized in laboratories all over the world. Notes: H and He are the building blocks of other naturally occurring elements

Trends in the Periodic Table Metals Alkali Metals Alkali Earth Metals Transition Metals Other (Rare) metals Metalloids Semi-conductors Non-metals Halogens Other Non-metals Noble Gas

Properties of Metals Conduct heat and electricity Luster – reflect light well Malleable – can be hammered or rolled into sheets Ductile – can be drawn into wire Ionic Bonding – when combined with non-metals Metallic Bonding – ions are sliding layers and electrons are weakly held

Alkali Metals Group 1: Soft, white, low-density, low-melting, highly reactive metallic elements Highly reactive with oxygen and water Uses: Human Health: sodium, potassium Photocells Francium – a radioactive element which breaks down giving off particles and energy

Alkali Earth Metals Group 2: Not found naturally in elemental form; two electrons in outer energy level. Much less reactive than Alkali Metals Uses: Strontium and magnesium found in fireworks Magnesium in vehicles, ladders and bats Calcium in statues and countertops Barium in disease diagnoses Radium formerly used in cancer treatment

Transition Metals Group 3-12: They are characterized by multiple valences, colored compounds, and the ability to form stable complex ions. Often occur in nature as uncombined elements Uses: Chromium – colored compounds, found in rubies and emeralds Iron – widely used, main ingredient in steel

Transition Metals (Continued) Uses: Cobalt and nickel – used in some steels Nickel – used to coat other metals Copper – used in electric wiring Silver – used in photographic film, jewelry Gold – used in jewelry Zinc and cadmium – used to coat and plate other metals Mercury – only room temperature liquid metal

Other / Rare Metals Any metal that is difficult to extract from ore and is rare and expensive commercially

Properties of Metalloid Between Metal and Non-metal Greek metallon = "metal“ and eidos = "sort". Form ionic and covalent bonds Have some metallic and some non-metallic properties Partial conduction give them “semiconductor” characteristics.

Semi-conductor Silicon in particular, which conducts electricity under certain conditions Computer chips and other electronic devices.

Properties of Non-Metals Usually gases or brittle solids at room temperature Not malleable or ductile Poor conductors of heat and electricity Usually not lustrous (shiny) Form ionic bond when combined with metals Form covalent bond with another non-metal

Hydrogen Most common element in the universe Diatomic molecule - H2 Highly reactive element found mostly on Earth as part of water compound

Halogen Group 17: Pure halogens exist as diatomic molecules, and they are highly reactive with Alkali Metal to form salt. Examples: bromine, iodine, fluorine, chlorine. Uses: Chlorine – disinfectant and bleach Bromine – dyes in cosmetics Iodine – hormone regulation, disinfectant

Noble Gas Group 18: They are monatomic (isolated) and chemically stable (inert). Also called inert gas. Uses: Helium – used in blimps and balloons Neon, argon, and krypton – used in lights

Atomic Radii Increasing Atomic Radius Increasing Atomic Radius

Atomic Radii Atomic Radii increase as you go down the group with increasing atomic number. Atomic Radii decrease as you go across the period with increasing atomic number. As proton number increases from left to right, the attraction to the nucleus becomes greater. Francium (Fr) is therefore the element with the largest atomic radius.