Chemistry Chemical Interactions Ch. 1

Bell Work 11/17/09 What is matter? What are the three states of matter? What is an atom?

Matter – is anything that has mass and takes up space. MATTER is never created or destroyed, it only changes form.

Atoms – The basic building blocks of all the substances in the universe. All things are made up of atoms. http://science.howstuffworks.com/nanotechnology1.htm

Elements – Are made of one kind. of atom grouped Elements – Are made of one kind of atom grouped together and cannot be broken down into simpler substances. Identical atoms make up elements 110 elements make up all the known substances on earth!!!

Atoms contain one or more PROTONS, NEUTRONS, and ELECTRONS

Electrons Protons and neutrons make up the nucleus of an atom. Electrons “float” around the nucleus of an atom. nucleus Electrons

Protons – Particles that have a positive electric charge. Neutrons – have no electric charge. Electrons – Particles with a negative charge located outside of the nucleus.

The nucleus of the atom is. positively charged (+). The The nucleus of the atom is positively charged (+). The negatively (-) charged electrons surround the nucleus to balance the charge of the atom to neutral. The number of protons equals the number of electrons.

Atomic number – the number of protons in an atom Atomic number – the number of protons in an atom. Found above the element symbol. Mass number – is equal to the number of protons plus the number of neutrons. The number of neutrons is determined by subtracting the atomic number from the mass number. Isotopes – atoms of the same element that have different numbers of neutrons.

The number in the right corner of each element represents the amount of protons that element has……thus the amount of electrons.

Groups – are the numbers at the top of the periodic table that represent the number of electrons in the outermost shell (energy level). Periods – the number to the left of the periodic table that represents the number of shells an element will have.

Electrons circle around the nucleus in shells or energy levels. As an element looses an electron it looses energy and as an element gains electrons it gains energy. Each circle or shell is limited to how many electrons it can hold.

Period number Group number

Valence electrons – electrons in the outermost energy level of an atom. The valence shell can have 1 to 8 electrons in it depending on its place on the periodic table. Elements to the left have 1 and elements to the right have 8.

Electrons in valance shells that are not full will either gain electrons to become full or give up electrons allowing its outer shell to be lowered to its next lowest level (which is full).