1. Basic Atomic Structure 12/10/12

2. Part I: Subatomic Particles subatomic particle = a particle found inside the atom. There are 3 types of subatomic particles: all atoms of all the different types of elements contain these same basic parts what makes one element different from another? The proton number. all atoms of the same element have the same proton number, and atoms of different elements have different proton numbers. ex: all gold (Au) atoms have 79 protons. 79 ≠ 47, so all silver (Ag) atoms have 47 protons. gold ≠ silver NameChargeSymbolLocationMass proton+1p+p+ in the nucleusapprox. 1 amu (1.007 amu) neutron0n0n0 in the nucleusapprox. 1 amu (1.008 amu) electrone-e- in electron cloud0.000 549 amu (negligible)

3. ex: all gold (Au) atoms have 79 protons. 79 ≠ 47, so all silver (Ag) atoms have 47 protons. gold ≠ silver neutron number varies with the type of isotope (more on this later) electron number is the same as proton number for uncharged (neutral) atoms (also, more on this later) Part II: Atomic Structure the atom has two distinct areas: the nucleus and the electron cloud. nucleus = center of the atom (like the core of the earth) where the protons and neutrons are found. the nucleus is positively charged. Why? Because of the presence of protons (see table in Part I above). the nucleus is the area of the atom with the most density remember, density = mass/volume look at the masses in the table in Part I above D = m V

4. the nucleus is the area of the atom with the most density remember, density = mass/volume look at the masses in the table in Part I above protons and neutrons are very heavy in relation to electrons (high mass) the area itself is very small (low volume) high mass/low volume = high density electron cloud = area surrounding the nucleus where the electrons are found, spinning very fast around the nucleus. the exact location of any particular electron cannot be known because of their high speed, but we do know that… electrons spin a distinct, confined distances from the nucleus (like planets have distinct orbits around the sun). We call these distinct distances from the nucleus “energy levels.” D = m V

5. electrons spin a distinct, confined distances from the nucleus (like planets have distinct orbits around the sun). We call these distinct distances from the nucleus “energy levels.” energy level = a distinct distance from the nucleus where an electron can be found, spinning. each energy level holds a different amount of electrons: 1st energy level holds 2 (total) 2nd energy level holds 8 (total) 3rd energy level holds 18 (8 outer, 10 inner) 4th energy level holds 32 (8 outer, 24 inner) the 5th – 7th energy levels hold even more than that

6. each energy level holds a different amount of electrons: 1st energy level holds 2 (total) 2nd energy level holds 8 (total) 3rd energy level holds 18 (8 outer, 10 inner) 4th energy level holds 32 (8 outer, 24 inner) the 5th – 7th energy levels hold even more than that in an electron dot diagram (AKA energy level diagram), only the outer electrons are shown. notice how the energy levels always contain paired, evenly distributed electrons.

7. Part III: Atom Symbols & Numbers all elements are represented by either 1- or 2-letter symbols. most match the name of the element, others come from old names or other languages. all symbols must either be one capital letter, or one capital and one lowercase. Identifies the element. atomic number = number of p +. Written in bottom-left-hand corner of symbol. Identifies the element. Identifies the isotope. mass number = number of p + & n 0. Identifies the isotope. Written in top-left-hand corner. average atomic mass = weighted average of all the mass numbers of all the isotopes of an element. Not written on symbol, but is found on PT. another number you can find on a symbol of an element is the charge. it will be located in the top right-hand corner of the symbol. we will discuss charge in more detail later.

8. Part IV: Isotopic Notation isotope = atoms of the same element that have the different numbers of neutrons. this means their proton number (atomic number) is the same, but because the number of neutrons differs, the result is different mass numbers for each isotope. ex: the isotope shown above is carbon-14. The other isotopes of carbon are carbon-12 and carbon-13. to find the neutron number of different isotopes, simply subtract the atomic number from the mass number. neutron number = mass number – atomic number

9. PRACTICE Draw a 6-row, 6 column table like this on your own paper. Label the top row as shown. Fill in the info that is given in red pen. Then fill in the info that is missing, per isotope, in pencil. Name of IsotopeSymbol Atomic Number Mass Number # of Neutrons # of Protons 910 66 Zn sodium-23 4020 ________-3216