ATOMS The smallest unit of an element that retains properties of the element.

History of the Atom Thomson John Dalton Described atom as a positive ball with negative electrons spread evenly throughout. Rutherford Said an atom had a positive nucleus with negative electrons orbiting it- it had NO NEUTRONS. John Dalton Matter is made up of atoms Atoms cannot be divided. All atoms of the same element are alike. Different elements are made of different atoms.

History of Atom continued- Electron Cloud Model Electrons form a cloud around the nucleus. This is the accepted model and allows for the unpredictable wave nature of electrons. Bohr Bohr’s model had a nucleus containing protons and neutrons. The electrons orbited on energy levels. This is the model we use in class.

Atomic Structure The smallest unit of an element is an atom. (Anything smaller is not an atom!) Atoms have 3 structural parts Protons Neutrons Electrons

Protons Have a positive charge Are located in the nucleus Atomic number Have a positive charge Are located in the nucleus Give an atom its identity Equal to the atomic number Chemical symbol Element Atomic mass

NEUTRAL NEUTRONS are in the NUCLEUS! Have NO charge (NEUTRAL) Are located in the nucleus Mass = protons + neutrons To determine the number of neutrons, subtract the number of protons (atomic number) from the atomic mass Round the atomic mass to nearest whole number (14.007 to 14) Subtract the number of protons from the mass (14 - 7) There are 7 neutrons The NEWS about atoms- NEUTRAL NEUTRONS are in the NUCLEUS!

Electrons Smallest, lightest particle Located outside the nucleus in the electron cloud Equal to the number of protons in a neutral atom (6th grade assumes all atoms are neutral) Negatively charged When drawing an atom, each shell or energy level is ONE row on the periodic table. (Row 1 has 2 elements- Energy level 1 has 2 electrons. Row 2 has 8 elements - Energy level 2 has 8 electrons.)

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 11 DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 11 DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 11 6 DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 11 6 DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 11 6 carbon DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Let’s Practice! (p6 in IA Notebook) element symbol atomic number atomic mass number of protons number of neutrons number of electrons boron B 5 11 6 carbon C 12 DON’T FORGET to ROUND the ATOMIC MASS!! REMEMBER Atomic number = protons Electrons = protons (in a neutral atom) Mass = protons + neutrons Chemical symbols are ALWAYS Capital/ lower-case letters!

Elements Simplest form of matter Made up of only ONE type of atom Atoms of an element are basically alike (ALWAYS have the same number of PROTONS), but the number of NEUTRONS may vary (ISOTOPES) Can be represented by a chemical symbol. (Chemical symbols are 1 - 2 letters. The first is always CAPITALIZED and second is LOWER-CASE) Some chemical symbols are from the elements’ Latin names

Isotopes of Hydrogen Atomic Number 1 Atomic Mass 1 Atomic Number 1

Most Common Elements There are a little over 100 elements found in nature. A limited number of those form the largest part of Earth’s crust, living matter, the oceans, and the atmosphere. Water- hydrogen and oxygen Air- nitrogen and oxygen Living things- carbon, hydrogen, and oxygen Earth’s crust- oxygen, aluminum, and silicon Most common elements are- aluminum, calcium, carbon, hydrogen, iron, magnesium, nitrogen, oxygen, potassium, silicon, sodium