Chapter Three

Dalton’s Atomic Theory: Every element is made of tiny, unique particles called atoms that cannot be subdivided Atoms of the same element are exactly alike Atoms of different elements can join to form molecules Because of new technology, we have discovered some holes in Dalton’s Atomic Theory

Breaking Down the Atom 1. Nucleus-center of an atom, all the mass of the atom is here it has a positive charge made up of protons and neutrons

Breaking Down the Atom 2. Protons-a positively charged particle It’s a subatomic particle has an atomic mass of 1 AMU 1. Neutrons-a neutral charged particle = NO CHARGE Subatomic particle same mass and size as a protons In reality, it is basically a proton that has neutralized its positive charge by absorbing an electron.

To Sum up the Nucleus The nucleus is made up of protons and neutrons. Protons and neutrons are both relatively the same mass and size but protons have a positive electrical charge and neutrons have no electrical charge.

Outside the Nucleus 1. Electron-a negative charged particle Very small mass ( AMU) Move around the nucleus because of the attraction btwn + and – charges Creates a “cloud” because the electrons are moving very fast.

Outside the Nucleus 2.Energy-level-this is a location where electrons can be found based on their energy. The more energy they have, the further away they are from the nucleus. Electrons can only be found in certain energy levels

Outside the Nucleus 3. Orbital-a region in an atom where there is a high probability of finding electrons. Electrons may occupy 4 distinct orbitals within atoms. *** Since all electrons are negatively charged, they repel each other, therefore they will always be as far away from each other and still fill an electron cloud. - Opposite Charges Attract, Like Charges Repel

Understanding the PTE Valence Electron- an electron in the outermost energy level of an atom Periodic Table of the Elements *This is a tool used by scientists to classify elements *It is not to be memorized, just applied Periodic law- properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number, or number of protons each has.

Periodic Table of the Elements Period- a horizontal row of elements in the periodic table. - 7 total rows - each represents the number of electron clouds in that element Group (family)-a vertical column of elements in the periodic table - All elements in a family have similar properties - All have the same number of valence electrons. - All usually will bond to the same cation(s) or anion(s)

Learning from the PTE Ionization-the process of adding electrons or removing electron from an atom -Atoms that do not have filled outer electron clouds can undergo a process called ionization. - This process results in a more stable atom. - Based on the position of the atom on the PTE.

Becoming Stable Ion-an atom or group of atoms that has lost or gained one or more electrons therefore has a net electric charge Cation-an ion with a positive charge - it loses an electron - it now will have more protons than electrons making it positive Anion-an ion with a negative charge - it gains electrons - it now has more electrons than protons

Information from the PTE Atomic number -the number of protons in the nucleus of an atom - The atomic number also equals the number of electrons it has. - Each element has a different atomic number Mass number -the total number of protons and neutrons in the nucleus of an atom - represents average of all the different atoms of an elements - The mass number includes only the number of protons and neutrons because protons and neutrons provide most of the atoms mass.

Exceptions to Daltons Rule Isotopes-any atoms having the same number of protons but different number of neutrons - Most elements have at least one different isotope - Hydrogen has three: 1.Normal- Hydrogen 1 2.Deuterium- Hydrogen 2 = 1 proton & 1 neutron 3.Tritium- Hydrogen 3 = 1 proton & 2 neutron ** this one is radioactive- glows in the dark

Finding out about the Atoms Atomic mass unit- represents the amount of mass of one proton of an element Average atomic mass- the weighted average of the masses of all naturally occurring isotopes of an element

Elements on the PTE Metals- the elements that are good conductors of heat and electricity - Most are shiny solids that can be stretched and shaped - are malleable- can be easily bent - Families can only loses electrons to form + ions Nonmetals- the elements that are not good conductors of heat and electricity - groups 13-18(approximately) - Nonmetals may be solids, liquids, or gases.

Metals Semiconductors- the elements that are intermediate conductors of heat and electricity Ex: Metalloids Alkali metals- the highly reactive metallic elements located in group 1 of the periodic table Ex. H, Na, Li, K, lose 1 e- to have a full valence shell ** most are dangerously explosive

Metals continued Alkaline earth metals- the reactive metallic elements located in group 2 of the periodic table Ex. Mg, Ca- Lose 2 e-s to fill their outer Electron cloud Transition metals- the metallic elements located in groups 3-12 of the periodic table * Have overlapping electron clouds * They are much less reactive then sodium or calcium, but they can lose electrons to form positive ions **VERY IMPORTANT – they cannot gain e-s

Halogens Halogens-the highly reactive elements located in group 17 of the periodic table - They gain 1 electron to have a full electron cloud - React very fast with group 1 metals Ex. Cl, Fl, Br and I

Kings of the PTE Noble gasses- the un-reactive gaseous elements (Group 18) * have full valence shells * happy atoms * Because these atoms have filled outer electron clouds, they do not need to lose or gain electrons to become stable.

Counting Atoms Mole-the SI base unit that describes the amount of substance * Mole day Avogadro's number- the number of particles in 1 mole equals 6.022x 10to the 23rd /mol Particles Molar mass- the mass in grams of 1 mole in a substance Conversion factor-a ratio equal to one that expresses the same quantity in two different ways 1 mole = 6.02*10to the 23rd particles