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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
Latin Names
Element Symbol Latin nameCopper Cu cuprumGold Au aurumLead Pb plumbumMercury Hg hydrargyrumPotassium K kaliumSilver Ag argentumSodium Na natriumTin Sn stannum
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
Particle Symbol Charge RelativeMass
Electron e- 1- 0
Proton p+ + 1
Neutron n 0 1
Subatomic Particles
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.
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
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 n8 e- 15 e- 30 e-
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
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 _______ _______ _______
Quick CheckAn 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
1) 30 2) 35 3) 65
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.
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.
Ion Illustration
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.
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
• 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.