Atoms, Elements, and Ions Chapter 1, Section 1 Atoms, Elements, and Ions

All matter is made of atoms. There are about 100 different elements that make up the majority of things around us. Atom: tiny particles that make up matter Element: made up of one type of atom Molecule: made up of more than one type of atom Hydrogen is the most common element in the universe, making up about 90%.

Atoms in Earth’s Crust Most oxygen (47%) and silicon (28%). Aluminum makes up about 8% and iron makes up about 5%. The rest is a mixture.

Atoms in Living Things Mostly oxygen (61%) and carbon (23%). Hydrogen makes up 10% and nitrogen makes up about 3%. The remaining 3% is a mixture.

Names/Symbols of Elements Each element has a unique name and symbol. For some, the symbol is the first letter: Hydrogen = H Oxygen = O Carbon = C For others, there are two letters. The first letter is always capitalized: Helium = He Zinc = Zn Calcium = Ca

Names/Symbols of Elements Some symbols refer to the element’s name in another language; Gold = Au (aurum) Lead = Pb Potassium = K Iron = Fe Copper = Cu

Dalton’s Theory John Dalton: each element is made up of its own type of atoms. All of the atoms in one element are identical to one another, but different than any other type of element’s atoms.

Atomic Structure The center of an atom = nucleus. Three types of subatomic particles: Protons: positive charge; located inside the nucleus Neutrons: no charge; located inside the nucleus Electrons: negative charge; located in orbits around the nucleus (electron cloud) Protons and neutrons are about the same size, and are much larger than electrons.

Atomic Numbers Atomic number: the number of protons inside the nucleus of an atom. This is how elements are arranged on the periodic table.

Atomic Mass Numbers Atomic mass number: total number of protons and neutrons in the nucleus All atoms of a certain element will always have the same number of protons; they may not have the same number of neutrons – changing the atomic mass number.

Isotopes When the number of neutrons changes in an atom, it creates an isotope: atoms of the same element with different neutron numbers. You can find the number of neutrons in an isotope by subtracting the atomic number from the atomic mass number.

Isotopes – Example Chlorine: All chlorine atoms have 17 protons. If chlorine-37 is an isotope, take 37 (atomic mass) and subtract 17 (atomic number) to figure out how many neutrons the isotope has. In this case, chlorine-37 has 20 neutrons.

Ions An atom has the same number of protons as it has electrons, making it have no charge. An ion is formed when an atom gains or loses an electron. The new atom becomes charged. If you lose an electron, you become positive. If you gain an electron, you become negative.

Positive Ions Positive ions are smaller than neutral atoms because they are losing electrons. Represented by the symbol name and + sign. If more than one electron is lost, include the number with the + sign.

Negative Ions Positive ions are larger than neutral atoms because they are gaining electrons. Represented by the symbol name and - sign. If more than one electron is lost, include the number with the - sign.

The Periodic Table of Elements Chapter 1, Section 2 The Periodic Table of Elements

Organizing Elements Mass number: the average mass of all of the element’s isotopes. Mendeleev, Dmitri: scientist who proposed the first periodic table of elements; organized them based on similar physical and chemical properties, as well as their mass numbers.

Modern Periodic Table of Elements Arranged by similar properties in columns, not rows. Arranged by atomic number, not atomic mass. Each element has a square, showing its atomic number, atomic mass, name, and chemical symbol.

Colors on the Periodic Table The letters of the symbol represent the physical state of the element at room temp. White = gas Blue = liquid Black = solid The background color represents whether it is a metal, nonmetal, or metalloid. Yellow = metal Purple = metalloid Green = nonmetal

Groups and Periods The elements in the same column form a group: these share similar physical and chemical properties; named by the number at the top of the column. Also called a family. The horizontal rows form periods: properties change from one end of the row to the other end.

Trends in the Periodic Table Ions: Atoms on the left side form positive ions easily; group 1 loses one electron, group 2 loses 2 electrons. Group 18 normally don’t form ions at all. Group 17 usually gains an electron, group 16 usually gains two. Size: As you move from left to right, atoms get smaller. As you move from top to bottom, atoms get larger. Density: Atoms at the top of a group are less dense; atoms at the ends of the periods (left and right sides) are less dense than those toward the middle.

Metals, Nonmetals, and Metalloids Chapter 1, Section 3 Metals, Nonmetals, and Metalloids

Regions on the Periodic Table Metals are mostly found on the left Nonmetals are mostly found on the right, with the exception of hydrogen Metalloids are found in between them

Most elements are Metals. Metals: conduct electricity and heat well, have a shiny appearance, are malleable (easy to shape), are mostly metals at room temp, except mercury. Examples: sodium (Na), copper (Cu), aluminum (Al)

Reactive Metals Alkali Metals can be found in group 1; they are very reactive. React rapidly with oxygen and water vapor Ions of these, like Na+ and K+, are important for life. Alkaline Earth Metals can be found in group 2; not as reactive as group 1, but more reactive than most metals. Calcium ions make up our bones and teeth. Magnesium is very light and used for building.

Transition Metals Elements in groups 3-12 are transition metals. Less reactive than most other metals; gold, silver, iron, and copper.