Chapter 1 Activity 4: Are Atoms Divisible?

(1 st Verse) They’re tiny and they’re teeny, Much smaller than a beany, They never can be seeny, The Atoms Family. (Chorus) (2 nd Verse) Together they make gases, And liquids like molasses, And all the solid masses, The Atoms Family (Chorus) They are so small. (snap, snap) They’re round like a ball. (snap, snap) They make up the air. They’re everywhere. Can’t see them at all. (snap, snap) (3 rd Verse) Neutrons can be found, Where protons hang around; Electrons, they surround The Atoms Family. (Chorus) (4 th verse) The periodic table, It isn’t just a fable; You’ll read it when your able; The Atoms Family (Chorus) (Chorus)

Democritus 1.Greek philosopher 2.He thought atoms were uncuttable 3. Therefore: Atoms are indivisible particles Atomos—Greek meaning ‘indivisible Ancient Greece B.C.

John Dalton—late 18 th century 1. What are atoms? 2. Do Carbon atoms differ from Oxygen atoms? Dalton’s Atomic Model: Hard, indivisible sphere Yes

HAS THIS EVER HAPPENED TO YOU?

Are there things inside the atom? YES! Subatomic particles- particles that are smaller than the atom e - p + n 0

Discovery of electron (e-) J.J. Thomson Cathode ray tube Discovered the electron in Identified a glowing beam of particles that traveled through a chamber of gas when exposed to an electrical current.

- This beam (cathode ray) was attracted to positive charges and repelled by negative charges. -Thomson concluded the beam must be composed of negatively charged particles. These came to be known as electrons.

Thomson’s Atomic Model “Plum Pudding” Model Negative electron plums are floating around in a sphere of positive pudding. ELECTRONS EMBEDDED WITHIN POSITIVE CHARGE

Discovery of the Nucleus Ernest Rutherford

Rutherford’s Au foil Experiment “+” charge Rutherford’s experiment Rutherford’s experiment -Discovered the Nucleus (through the Gold Foil Experiment) -Discovered that the atom is mostly empty space -Alpha particle: a positively charged particle, consisting of two protons and two neutrons (helium nucleus).

Rutherford’s Nuclear Atom Positive Nucleus Negative electrons surround nucleus amidst lots of empty space.

Discovery of the proton Eugen Goldstein In 1886, Goldstein observed rays in a cathode ray tube that traveled oppositely than the electrons previously discovered.

James Chadwick 1. Discovered the neutron in This subatomic particle is heavy enough to split a nucleus 3. Led the way to the creation of the atomic bomb

Protons Located in nucleus Determine which element (DNA) # of protons = atomic number equal to # of electrons in a neutral atom equal to # of electrons in a neutral atom Ch 1: Activity 4

LETS HAVE SOME PRACTICE 6 C Carbon 12 Atomic Number (Protons) Mass Number (Proton+Neutrons) Element Symbol Element Name 12 6 Mass Number (Protons+Neutrons) Atomic Number (Protons) C

Mass Number Almost all the mass of an atom comes from protons & neutrons # Protons + # Neutrons = mass number

Atomic # = # of protons (P) # protons = # electrons in an atom # protons = # electrons in an atom Mass # = number of protons and neutrons (P + N) So,to get the # of neutrons we must Subtract Atomic # from the Mass # = # Neutrons REVIEW TIME 12 6 C 6 neutrons

Practice Determine the # of protons,neutrons, & electrons ProtonsNeutronsElectrons He B Mg ZnProtonsNeutronsElectronsHe222 B Mg ZnProtonsNeutronsElectronsHe B565 Mg ZnProtonsNeutronsElectronsHe B Mg ZnProtonsNeutronsElectronsHe B Mg Zn303530

Subatomic Particles Electron: e - negative charge negative charge 9.11 x kg 9.11 x kg Proton: p + positive charge positive charge 1.67 x kg 1.67 x kg Neutron: n 0 no charge no charge 1.67 x kg 1.67 x kg

What did Battleship teach us? Battleship simulated Rutherford’s Gold Foil Experiment. RutherfordBattleship Alpha Particles Your missiles Nucleus Pattern Drawn Atom is mostly empty space All of the empty boxes

Atoms vs Ions ATOMSIONS Protons = Electrons Protons ≠ Electrons Cations= More Protons Positive Charge Anions= More Electrons Negative Charge

IONS cation (+) anion (-) Li +1 Cl -1 3 Protons 2 Electrons 17 Protons 18 Electrons Can’t Change the Number of Protons

Ions An ion is an atom with a positive (+) or negative (-) charge Atoms that gain electrons have - charges Atoms that lose electrons have + charges

Isotopes Atoms of an element can have different numbers of neutrons – these are isotopes The number of protons is always the same, but since more neutrons add more mass, the mass number can be different

Isotopes Protons = Protons BUT……#Neutrons are Different So Mass # is Different AtomProtonsNeutronsElectrons Mass # Carbon Carbon Carbon

Isotopes

Atoms are really small

How Big Is An Atom?

The Scale of the Universe Virtual Atom Ted Talk: How Small is an Atom Ted Talk: How Small is an Atom

Practice The atomic number of an atom is always equal to the total number of:The atomic number of an atom is always equal to the total number of: a. Neutrons in the nucleus b. Protons in the nucleus c. Neutrons plus protons in the nucleus d. Protons plus electrons in the atom

Practice If the number of electrons and protons are not equal:If the number of electrons and protons are not equal: a. an atom exists b. an isotope exists c. an ion exists d. None of the above

Practice An atom that has lost electrons has what type of charge?An atom that has lost electrons has what type of charge? POSITIVE POSITIVE Once it has lost electrons it is no longer an atom. What is it called?Once it has lost electrons it is no longer an atom. What is it called? CATION

Practice An atom of 42 Ca contains:An atom of 42 Ca contains: a. 20 protons and 22 neutrons b. 20 protons and 42 neutrons c. 20 electrons and 42 neutrons d. 20 electrons and 22 protons

Practice Atoms that have the same atomic number but different mass numbers are called?Atoms that have the same atomic number but different mass numbers are called? isotopes isotopes

Practice Look at the picture below and then fill in the chart:Look at the picture below and then fill in the chart:AtomProtonsNeutronsElectrons Mass # Lithium-6 Lithium-7 Lithium

Practice The nucleus of an Fe-56 atom contains:The nucleus of an Fe-56 atom contains: a. 26 protons, 30 neutrons and 26 electrons b. 26 protons, 26 neutrons and 30 electrons c. 26 protons and 56 neutrons d. 26 protons and 30 neutrons

Practice What did Rutherford’s Gold Foil experiment discover?What did Rutherford’s Gold Foil experiment discover? a. electron b. neutron c. nucleus d. proton

Practice A 52 Cr 3+ ion contains:A 52 Cr 3+ ion contains: a. 24 protons, 52 neutrons, 21 electrons b. 24 protons, 28 neutrons, 24 electrons c. 24 protons, 28 neutrons, 27 electrons d. 24 protons, 28 neutrons, 21 electrons

Practice What is the total number of electrons in an atom with an atomic number of 30 and a mass number of 65?What is the total number of electrons in an atom with an atomic number of 30 and a mass number of 65? a. 30 b. 65 c. 35 d. 95

Practice Who discovered the electron and how?Who discovered the electron and how? a. Democritus, atomic theories b. Dalton, cathode ray tube c. Rutherford, gold foil experiment d. Thomson, cathode ray tube