Physical Science Jones Chapter 4 Atoms & The Periodic Table

What will we be learning? Section 1 – Atomic Structure Explain Dalton’s Atomic Theory, and describe why it was more successful than Democritus’ theory. State the charge, mass, and location of each part of an atom according to the modern model of an atom. Compare and contrast Bohr’s model with the modern model of the atom.

Inquiry learning! Read pages Write down important names, dates, and discoveries of parts of the atom. On a piece of copy paper, draw a timeline and include the important names, dates, and experiments in order. Be sure to include information about the following people and their discoveries: John Dalton Democritus Niels Bohr

Atomic Theory What did the scientists think the atom looked like? It was too small to see There was not a lot of technology to “look” at atoms (microscopes, etc.)

400 BC: Atomic theory The idea of matter existing as particles was introduced as early as 400 B.C. Democritus – atoms are “indivisible” Aristotle – all matter was continuous Aristotle’s proposal lasted about 2000 years

1808: Dalton’s atomic theory John Dalton, 1808 – proposed an explanation for the previous laws: 1. All matter is composed of extremely small particles called atoms 2. Atoms of a given element are identical in size, mass, and other properties 3. Atoms cannot be subdivided, created, or destroyed 4. Atoms of different elements combine in simple, whole- number ratios to form compounds 5. In chemical reactions, atoms are combined, separated, or rearranged

~100 years after Dalton Scientists decided that Dalton’s #3 was incorrect: “Atoms cannot be subdivided.” We now know there are subatomic particles (parts of an atom) Proton Neutron Electron

1913: Niels Bohr Danish Scientist Said electrons move around the nucleus (where the protons and neutrons are) like planets orbiting the sun

1925 Scientists believed that electrons moved more like waves than particles that orbit the nucleus

Modern Atomic Theory What do we believe about what the atom looks like now? Dalton’s atomic theory + subatomic particles Atoms have a nucleus Cluster of protons + neutrons Atoms have an electron cloud Electrons surround the nucleus in various energy levels Are in motion Location of an electron cannot be determined

Energy levels Electrons are found in energy levels around the nucleus Often described like rungs of a ladder Outermost energy level has a certain number of electrons called valence electrons Atoms can lose or gain valence electrons to become more stable Atoms that have lost or gained electrons are called ions

Good Afternoon! Please review last week’s content by completing the following: P 110 #1-6 P 119 #1-5

What will we be learning? Section 2 & 3 – The Periodic Table Relate the organization of the periodic table to the arrangement of electrons within an atom. Explain why some atoms gain or lose electrons to form ions. Determine how many protons, neutrons, and electrons an atom has, given its symbol, atomic number, and mass number. Describe how the abundance of isotopes affects an element’s average atomic mass.

The Periodic Table The elements are not put on the table in a random order. Listed by atomic number Arranged by number of valence electrons, reactivity, and other characteristics Period = row Group = column Elements in the same group have the same characteristics because they have the same number of valence electrons

_______________________ Element Name _______________________ Mass Number ____________________ Atomic Number # of Protons: ________ # of Electrons: _______ # of Neutrons: _______

The Periodic Table # of protons = atomic number # of electrons = # of protons (because the atom is neutral) # of neutrons = rounded mass number - # of protons Classwork! Complete the worksheet – use the periodic table to indicate the symbol and number of subatomic particles for each element.

Ions Ions – atoms of elements that have either lost or gained electrons Cation – a positive ion that has lost electrons Anion – a negative ion that has gained electrons Atoms lose or gain electrons to become more stable. Each atom gains enough to have 8 valence electrons, or loses enough to have a full outer energy level. Ca: 2 valence electrons – lose them, or gain 6? Lose them = Ca +2 N: 5 valence electrons – lose them, or gain 3? Gain 3 = N -3

Isotopes Isotopes - Atoms of an element with a different number of neutrons Different number of protons = not ok! (different element) Different number of electrons = not ok! (ions) Elements exist in different forms with different masses on Earth. Example: H-1: “Hydrogen-1” with 1 proton, 1 electron, 0 neutrons. H-2: “Hydrogen-2” with 1 proton, 1 electron, 1 neutron. H-3: “Hydrogen-3” with 1 proton, 1 electron, 2 neutrons.

Isotopes The mass of each isotope is calculated in to the mass number found on the periodic table The average atomic mass is the average of the mass numbers and their percentage of abundance on earth. The average atomic mass is an average mass of ALL THE ATOMS of that element found on earth. Unit: atomic mass units (amu)

The Periodic Table Three groups of elements: Metals Nonmetals Semiconductors (also called Metalloids)

Parts of the Periodic Table Label and color each of the following: Alkali Metals – Group 1 EXCEPT FOR HYDROGEN Alkaline-earth Metals – Group 2 Transition Metals – Groups 3 – 12 (middle of the table) Nonmetals – Hydrogen, Groups 17-18, O, S, Se, N, P, and C Halogens – Group 17 Noble Gases – Group 18 Semiconductors/metalloids – B, Si, Ge, As, Sb, Te The rest are just called “other metals”

Parts of the Periodic Table Metals Conductors of electricity Shiny Can be made into wires Alkali metals are most reactive Alkaline-earth metals are found in the human body Transition metals are less reactive but very useful

Parts of the Periodic Table Nonmetals Cannot conduct electricity or be made into wires Can form many compounds, especially carbon Plentiful on earth Halogens are very reactive Noble gases do not react at all

Parts of the Periodic Table Semiconductors/Metalloids Have some properties of metals and some properties of nonmetals Are very useful Silicon is most familiar Makes up sand (SiO 2 ) Found in 28% of the mass of Earth’s crust Used in computer parts

What will we be learning? Section 4 – Using Moles to Count Atoms Explain the relationship between a mole of a substance and Avogadro’s constant. Find the molar mass of an element by using the periodic table. Solve problems converting the amount of an element in moles to its mass in grams, and vice versa.

Counting Units What units are used in chemistry to measure a substance? Grams (mass) – measured by a scale Moles (a large counting unit) – cannot be measured by a scale, but can be calculated using mass A small number with a large unit Atoms (a small counting unit) – cannot be measured by a scale, but can be calculated using moles A large number with a small unit

Mass, in grams Mass – a measure of the amount of matter Molar Mass – the mass of 1 mole of a substance The molar mass of any element = its mass number How many grams are in 1 mole of Carbon? How many grams are in 1 mole of Aluminum?

Mass, in grams Mass – a measure of the amount of matter Molar Mass – the mass of 1 mole of a substance The molar mass of any element = its mass number How many grams are in 1 mole of Carbon? g How many grams are in 1 mole of Aluminum? g

Mass, in grams Mass – a measure of the amount of matter Molar Mass – the mass of 1 mole of a substance The molar mass of any element = its mass number How many grams are in 1 mole of Carbon? g How many grams are in 1 mole of Aluminum? g The molar mass of any compound = mass numbers added together How many grams are in 1 mole of H 2 O? How many grams are in 1 mole of Na 2 SO 4 ?

Mass, in grams Mass – a measure of the amount of matter Molar Mass – the mass of 1 mole of a substance The molar mass of any element = its mass number How many grams are in 1 mole of Carbon? g How many grams are in 1 mole of Aluminum? g The molar mass of any compound = mass numbers added together How many grams are in 1 mole of H 2 O? = 18 g How many grams are in 1 mole of Na 2 SO 4 ? = 142 g

Avogadro’s Constant 1 mole of ANYTHING = x particles = 602,200,000,000,000,000,000,000 particles Particles = atoms = molecules How many atoms are in 1 mole of Carbon? How many molecules are in 1 mole of Na 2 SO 4 ?

Avogadro’s Constant 1 mole of ANYTHING = x particles = 602,200,000,000,000,000,000,000 particles Particles = atoms = molecules How many atoms are in 1 mole of Carbon? x atoms How many molecules are in 1 mole of Na 2 SO 4 ? x molecules

Conversions A calculation that changes one unit to another unit Mass  Moles Use the molar mass of the substance in the problem (How many grams are in 1 mole of _______?) P 133 #1-4 P 134 #1-9 Turn it into the drawer when you are finished.

Good Afternoon! Honors Physical Science Bellwork – P 133 #1-4, P 134 #6-9 Converting between mass and moles Hint: given is moles, answer is in grams– multiply given by the molar mass Hint: given is grams, answer is in moles – divide given by the molar mass Check your answers with me before you turn it in. Be sure to show all work and circle your answers!

Chapter 4 Wrap-Up Do P 136 #1-18, 20-21, 31 Turn into the drawer when you are finished.