CHEMICAL INTERACTIONS Ch 1.1 Atoms are the smallest forms of elements

ATOMS All matter is made of tiny particles called atoms. All atoms have a core called a nucleus. The nucleus contains protons and neutrons.

PROTONS & NEUTRONS Protons are particles with positive electric charges (+). Neutrons are particles with no electric charges. Protons and neutrons have similar masses and together make up the mass of an atom.

ELECTRONS An electron has a negative charge (–) and a very small mass. Electrons move so fast it is hard to pinpoint their location. Not all electrons in an electron cloud have the same energy.

ELECTRON ENERGY LEVELS In atoms, electrons are at fixed energy levels. The 1 st energy level is closest to the nucleus and holds up to 2 electrons. The 2 nd level holds eight, the 3 rd holds up to 8 or 18. Higher levels hold up to 8 or up to 32 or more.

Draw correct number of electrons ELECTRON ENERGY LEVELS Example:

MASS OF AN ATOM The mass of a proton is much greater than the mass of an electron. The positive charge of a proton is equal to the negative charge of an electron. In a neutral atom there are equal numbers of protons and electrons.

PARTS OF AN ATOM P N A B C D E

PARTS OF AN ATOM P N A: NUCLEUS B: PROTONS C: NEUTRONS D: ELECTRON CLOUD 2 8 Up to 8 or 18 Up to 8 or 32 ENERGY LEVELS

Circle your level of understanding of these concepts: 1234

ELEMENTS & CHEMICAL SYMBOLS

ELEMENTS Elements are made of only one type of atom. Oxygen, carbon, and hydrogen are examples of elements. Example: Carbon is made of only carbon atoms.

CHEMICAL SYMBOLS The name of an element can be represented by a chemical symbol. When one letter is used as a symbol it is a capital letter. Example: oxygen is O, hydrogen is H, & carbon is C...

When a symbol contains two letters, the 1 st letter is a capital and the 2 nd is in lower case. Example: helium is He, chlorine is Cl, & lithium is Li. Most symbols come from the English name of the element; some come from the Latin name.

The symbol is the one or two letter abbreviation for the element. The element name is the chemical name given to a substance. O * Oxygen Cl * Chlorine K * Potassium Na * Sodium S * Sulfur

SYMBOL BOX He 2 Helium 4.00 Atomic number Symbol Element name Atomic mass

SYMBOL BOX

Atomic number: the number of protons in an atom found in the nucleus. Helium has two protons, so its atomic number is 2. Atomic mass: the average number of protons and neutrons in an atom. This is the relative mass of the element compared to carbon as a standard.

Atomic Number = # of Protons = # of Electrons Mass number: total number of protons and neutrons in an atom. ATOMIC MASS (AVERAGE- DECIMAL) MASS NUMBER (WHOLE NUMBER) = # of Protons + # of Neutrons OR = # of Electrons + # of Neutrons OR = Atomic Number + # of Neutrons Subtracting the # of protons (atomic # or # of electrons) from the mass number, will give you the # of neutrons.

PERIODIC TABLE Dmitri Mendeleev, a Russian scientist, arranged the elements into the Periodic Table. Certain chemical properties were repeated regularly. These properties were related to the sum of the protons and neutrons in an atom. By the middle of the 19 th century, a number of elements had been discovered.

Mendeleev’s table contained the 65 elements then known and blank spots where he predicted the properties of elements not yet discovered. Some problems occurred with his arrangement. As a result, today’s classification system is based on the atomic numbers of elements. This organization of elements is called the PERIODIC TABLE.

PERIODIC TABLE Scientists have discovered 118 substances called elements. 92 of these occur naturally, the rest are made in laboratories. An element is a substance that cannot be broken into smaller substances.

ISOTOPES Atoms of the same element ALWAYS have the same number of protons. All atoms of the same element do NOT always have the same number of neutrons. Isotopes: atoms of the same element with different numbers of neutrons.

METALS H hydrogen Na sodium Mg magnesium K potassium Ca calcium Ba barium Fe iron Zn zinc Ag silver Cu copper Mn manganese Li lithium Pb lead Ni nickel Co cobalt Au gold Al aluminum Sn tin Hg mercury

NON-METALS Cl chlorine F fluorine Br bromine O oxygen S sulfur I iodine N nitrogen P phosphorus He helium B boron Si silicon Ne neon Rn radon C carbon Xe xenon Ar argon