# Atoms - Rathjen Science! Atoms Atomic Structure Electrons negatively charged part of atom found in electron clouds Nucleus positively charged center Protons positively charged particles in the

nucleus Neutrons particles in the nucleus that have no charge; neutral Charge of protons and electrons are opposite but equal, so their charges cancel each other out. Atoms of different elements contain different numbers of

protons Atomic Number number of protons in an atom Ex: Carbon atomic number is 6 6 protons, 6 electrons Atomic Number Element Name 6 C

Carbon 12.0 Chemica l Symbol Atomic Mass or Mass Number Copy this chart in your notes. Use the periodic table to fill in the missing info. Element Name

Atomic Number Chemical Symbol Atomic Mass Hydroge n Fe 8 12.0 Aluminu Atomic Mass/Mass Number Total

number of protons and neutrons in an atom. Ex: Carbon mass number is 12, atomic number is 6. 12 6 = 6 There are six neutrons. Example Boron 1. Atomic Number is 5 Atomic Mass is 11 (10.81 rounds to 11) Protons = 5 Electrons = 5

Neutrons = 11-5 = 6 Group Lets draw the Boron atom: 5 protons 5 electrons

6 neutrons electro ns - - +++ N + + N NNN N - Nucleus protons and

neutrons - Quick Check! Draw a NITROGEN atom with the correct number of protons and neutrons in the nucleus and the correct number of electrons in the electron cloud. Quick Check! Draw a Fluorine atom with the correct number of protons, neutrons, and electrons. -

+ + + + + + + N+ + - - N NN N N N N N N - -

- Isotopes Isotopes are atoms of the same element that have different numbers of neutrons. Ex: Carbon (C) atoms Always have 6 protons Naturally occurring Isotopes of carbon

6 neutrons (most common) 7 neutrons 8 neutrons Mass of an Atom The mass is so small that scientists made up a new unit. Atomic Mass Unit (amu) 1 proton ~ 1 amu 1 neutron ~ 1 amu

1 electron ~ 0 -> the mass of electrons has very little effect on the atoms total mass Mass Number = # of Protons + # of Neutrons Ex: Carbon Mass Number = 6 protons + 8 neutrons

Mass Number = 14 Carbon-14 Carbon -13 Carbon-12 (most common) Ex2: How many protons, neutrons, and electrons are in Neon22? Atomic Number = 10 Protons = 10 Protons 10 + Neutrons = Mass Number + ______

= 22 Neutrons = 12 How many electrons are in this isotope? 10 Ex3: How many protons, neutrons, and electrons are in Nitrogen-15? Atomic Number = 7 Protons = 7 Electrons = 7 Neutrons = 8 Protons 7 + Neutrons = Mass Number +

Neutrons = 8 _______ = 15 Unstable or Radioactive Isotopes Some isotopes are unstable or radioactive atoms that spontaneously fall apart after a certain amount of time, giving off radiation. Radiation can damage or destroy living cells. Radioactive Isotopes Cobalt 60

Protons: 27 Neutrons: 33 Electrons: 27 Mass Number: 60

Use: irradiating food (kills bacteria) The more neutrons in an isotope, the more mass it has, the easier it is to break apart the more likely it is radioactive Half-life the time it takes an atom to decay Isotopes may also be written like this 3

He Helium-3 Na Sodium-23 23 Mass number Quick Check! What is the name of this isotope? (Draw a diagram of this isotope in your notebook.)

Proton s Neutro ns Electro ns Particle Accelerator (Atom Smasher) used to make synthetic (man made) atoms Ions Ions an atom that is no longer neutral because it has gained or lost electrons

Positive ions when electron(s) are lost -more protons than electrons Helium N + + N - Negative ions when electron(s) are added or gained -more electrons than protons Helium N

+ + N - - Ex1: Positive or Negative Ion? - N N +

+ + N - Positive ion Why? B/c there are more protons than electrons (more positive than negative charges) Which element? Lithium Li+ Ex2:

Negative Ion?- Positive or N N + + + + - N N

N + - Positive ion How many electrons were lost? 2 Which element? Boron B2+ - Ex3: Negative Ion?-

Positive or N N - N + + + - +

N N - + - Negative ion How many electrons were added? 1 Which element? Boron B-