CHEMISTRY G10 SEM I

Chemistry

The study of matter and the changes it undergoes

Matter

Anything that has mass and takes up space

Chemical reaction

The process by which the atoms of one or more substances are rearranged to form substances

Atomic theory is divided into

five:

-Early Theory

-Democritus’ Theory

-Aristotle’s Theory

-Dalton’s Theory

-Modern Theory

Early Theory states that

Matter is made up of water, fire, air, and earth

Democritus’ theory states that

Matter is composed of empty spaces through which atoms can move

Aristotle’s theory states that

Rejected Democritus’ theory entirely and did not believe the nothingness of empty space

Dalton’s theory states that

All matter is composed of tiny particles called atoms

Modern theory states that

Atoms:

-are divisible

-have different mass

-of the same element can combine to form molecules

-can be created or destroyed

The law of conservation of mass states that

Mass cannot be created or destroyed during a chemical reaction, but it is conserved

The law of definite proportions states that

Regardless the amount, a substance always consists of the same elements in the same proportion by mass

The law of multiple proportions states that

When different compounds are formed by the combination of the same elements, different masses of one element combine with the same mass of the other element in a ratio of the smallest whole numbers

Atom

The smallest particle of an element that retains the properties of the element

Nucleus

An extremely small, positively charged, dense center of an atom that contains positively charged protons, neutral neutrons, and is surrounded by an empty space through which one or more negatively charged electrons move

Electron

A negatively charged, fast-moving particle with an extremely small mass, that is found in all forms of matter, and moves through the empty space surrounding an atom’s nucleus

Proton

A subatomic particle in an atom’s nucleus that has a positive charge of 1+

Neutron

A neutral subatomic particle in an atom’s nucleus that has a mass nearly equal to that of a proton

Atomic number

Number of protons in an atom

Isotopes

Atoms of the same element with the same number of protons and different number of neutrons

Mass number

The number after the element’s name, representing the sum of the proton and neutron

Atomic orbital

A three-dimensional region around the nucleus of an atom that describes an electron’s probable location

Principal quantum numbers

Indicates the relative sizes and energies of atomic orbitals

Principal energy levels

The major energy levels of an atom

Electron configuration

The arrangement of electrons in an atom

Valence electrons

Electrons in the atom’s outermost orbitals — generally those orbitals associated with the atom’s highest principal energy levels

Electron-dot structure

Consists of the element’s symbol, which represents the atom’s nucleus and inner-level electrons, surrounded by dots representing the atom’s valence electrons