Chap 4 Bell -Ringers

The Structure of the Atom The Atom has a Structure

What we’ve seen so far… Chapter 1 The Science of Chemistry - Chemistry is about discovering and understanding natural laws using the scientific method - Energy cannot be created nor destroyed Chapter 1 The Science of Chemistry

What we’ve seen so far… Chapter 1 Chapter 2 The Science of Chemistry - Matter can be mixtures or substances. The smallest unit of a pure substance is an element. - Each element is a type of atom, and they can be arranged in a periodic table. - Atoms come together to form compounds. Atoms with an electric charge are known as ions. Chapter 1 The Science of Chemistry Chapter 2 Matter and Atoms

What we’ve seen so far… Chapter 1 Chapter 2 The Science of Chemistry Matter and Atoms Chapter 3 Temperature, Energy, and Heat - Temperature is a measure of kinetic energy. - Heat is thermal energy. - Heat gain and heat loss can cause phase changes, as molecules are rearranged.

What we’ve seen so far… Chapter 1 Chapter 2 The Science of Chemistry Matter and Atoms Temperature, Energy, and Heat Physical and Chemical Change - In a physical change molecules are rearranged. In a chemical change atoms are rearranged to make new substances. - Chemical reactions can be endothermic or exothermic. - Many reactions occur in aqueous solution, and some elements are more reactive than others.

How can we explain the properties and behaviors observed so far? Chapter 1 The Science of Chemistry Chapter 2 Matter and Atoms Temperature, Energy, and Heat Physical and Chemical Change How can we explain the properties and behaviors observed so far?

Answers can be found inside the atom Chapter 1 The Science of Chemistry Chapter 2 Matter and Atoms Chapter 3 Temperature, Energy, and Heat Physical and Chemical Change How can we explain the properties and behaviors observed so far?

92 different types of atoms!

Each of the elements is a unique type of atom. Atoms are made from smaller particles! protons neutrons electrons Each of the elements is a unique type of atom.

How did scientists come up with this? Atoms are made from smaller particles! protons neutrons electrons How did scientists come up with this?

It started a long time ago… 460 – 370 BC Today Democritus Beginning of Atomism You cannot divide something in half forever. The smallest piece of matter is called an atom.

Think of the Rutherford marble tossing lab How do you find out about something you can’t see? Think of the conservation of mass labs, distilled wood, even flame test lab Think of experimentation of the Copper, HCl and Zinc lab Think of the Rutherford marble tossing lab

Bellringer When scientists wanted to find out what an atom was, they were not able to look directly at what the atom was made of. They had to make inferences from the results of many different experiments. It was like trying to describe a picture, such as the one on the next slide, with only small portions visible.

Bellringer, continued 1. Write four sentences describing what you can see of the above picture. 2. What information or parts of the picture would make your descriptions more accurate without revealing the entire picture?

Scientists contributing CHADWICK THOMSON RUTHERFORD DALTON de BROGLIE BOHR

1. All elements are made of tiny indivisible particles called atoms. Dalton’s Postulates 460 – 370 BC 1808 Today 1. All elements are made of tiny indivisible particles called atoms. Democritus Atomism Over 2,000 years later John Dalton comes up with the first “modern” atomic theory.

1. All elements are made of tiny indivisible particles called atoms. Dalton’s Postulates 460 – 370 BC 1808 Today 1. All elements are made of tiny indivisible particles called atoms. Democritus Atomism 2. All atoms of the same element are the same, but different from atoms of every other element. Over 2,000 years later John Dalton comes up with the first “modern” atomic theory.

1. All elements are made of tiny indivisible particles called atoms. Dalton’s Postulates 460 – 370 BC 1808 Today 1. All elements are made of tiny indivisible particles called atoms. Democritus Atomism 2. All atoms of the same element are the same, but different from atoms of every other element. Over 2,000 years later John Dalton comes up with the first “modern” atomic theory. 3. Chemical reactions rearrange atoms but do not create, destroy, or convert atoms from one element to another.

1. All elements are made of tiny indivisible particles called atoms. Dalton’s Postulates 460 – 370 BC 1808 Today 1. All elements are made of tiny indivisible particles called atoms. Democritus Atomism 2. All atoms of the same element are the same, but different from atoms of every other element. Over 2,000 years later John Dalton comes up with the first “modern” atomic theory. 3. Chemical reactions rearrange atoms but do not create, destroy, or convert atoms from one element to another. 4. Compounds are made from combining atoms in simple whole number ratios.

Another kind of light? 460 – 370 BC 1808 1870 Today Democritus Atomism Dalton “Modern” atomic theory William Crookes invents a tube in which virtually all the gas has been removed. Under high voltage, a ray was emitted from the cathode end of the tube.

Cathode rays must be negative. It started a long time ago… 460 – 370 BC 1808 1870 1897 Today Democritus Atomism Dalton “Modern” atomic theory Crookes Cathode rays J.J. Thomson discovers the electron Cathode rays must be negative.

It started a long time ago… 460 – 370 BC 1808 1870 1897 1910 Today Democritus Atomism Dalton “Modern” atomic theory Crookes Cathode rays Thomson Discovery of the electron Ernest Rutherford discovers the nucleus

Size and mass The size of the atom comes mostly from the space occupied by the electrons The mass of the atom comes mostly from the nucleus

Charges in the atom neutrons protons electrons

Charges in the atom A complete atom has a charge of zero

Charges in the atom

What happens when you change the number of protons? neutrons protons electrons What happens when you change the number of protons?

You obtain a different element! 6 protons in carbon 7 protons in nitrogen 8 protons in oxygen You obtain a different element! The number of protons is also called the atomic number for that element.

The electron cloud Electrons are very light and fast. They are not organized along orbits around the nucleus. Except for mass, virtually every property of atoms is determined by electrons, including size and chemical bonding

What happens when you change the number of neutrons? protons electrons What happens when you change the number of neutrons?

They hold protons together in the nucleus. Atomic number Neutrons act as “glue.” They hold protons together in the nucleus.

12C Mass number = 6 p + 6 n = 12 “carbon-12” mass number: total number of protons and neutrons in a nucleus.

Name Mass number # protons # neutrons

Carbon-12 Carbon-13 Carbon-14 Name Mass number # protons # neutrons

Carbon-12 Carbon-13 Carbon-14 Name Mass number 12 13 14 # protons # neutrons

Carbon-12 Carbon-13 Carbon-14 Name Mass number 12 13 14 6 6 6 # protons # neutrons

Carbon-12 Carbon-13 Carbon-14 Name Mass number 12 13 14 6 6 6 # protons 6 7 8 # neutrons

isotopes: atoms or elements that have the same number of protons in the nucleus but different number of neutrons.

How can lithium have 0.941 neutrons? Two lithium isotopes in nature Atomic mass How can lithium have 0.941 neutrons?

Number of neutrons for each of 100 lithium atoms randomly sampled from nature It’s an AVERAGE mass!

Isotope periodic table (first 4 rows)

There must be a force that keeps the nucleus together Forces in the atom There must be a force that keeps the nucleus together

Electrons form bonds between atoms. Forces in the atom In the nucleus Electrons The strong nuclear force attracts protons to protons, neutrons to neutrons, and protons to protons Electrons repel each other, but don’t “fall into” the nucleus because they are in constant motion. Electrons form bonds between atoms.

The size of the atom comes mostly from the electrons 460 – 370 BC 1808 1870 1897 1910 Today Democritus Atomism Dalton “Modern” atomic theory Crookes Cathode rays Thomson Discovery of the electron Rutherford Discovery of the nucleus electrons protons neutrons The size of the atom comes mostly from the electrons The mass of the atom comes mostly from the nucleus

Who coined the term atom in 4 BC? Dalton Democritus Rutherford Bohr Thomson

Who stated that elements are made of indivisible spheres called atoms? Dalton Chadwick Rutherford Bohr Thomson

Who discovered the atom was divisible and had subatomic parts? Dalton Chadwick Rutherford Bohr Thomson

Who discovered the electron? Dalton Chadwick Rutherford Bohr Thomson

Who discovered that atoms are mostly empty space? Dalton Chadwick Rutherford Bohr Thomson

Who discovered the nucleus? Dalton Chadwick Rutherford Bohr Thomson

Who discovered the proton in the nucleus? Dalton Chadwick Rutherford Bohr Thomson

Who stated that electrons are located in fixed energy levels? Dalton Chadwick Rutherford Bohr Thomson

Who discovered the neutron? Dalton Chadwick Rutherford Bohr Thomson

Center of a atom, contains most of the atom’s mass Proton Neutron Electron Nucleus Energy levels Mass number Electromagnetic force

Positively charged particle that exists in the nucleus of an atom. Proton Neutron Electron Nucleus Energy levels Mass number Eelctromagnetic force

Particle with no charge that exists in the nucleus of an atom Proton Neutron Electron Nucleus Energy levels Mass number Electromagnetic force

The least massive of the three subatomic particles which also carries an negative net charge. Proton Neutron Electron Nucleus Energy levels Mass number Electromagnetic force

Describes how electrons are arranged around an atom Proton Neutron Electron Nucleus Energy levels Mass number Electromagnetic force

The force that holds the positively charged nucleus together is called Proton Neutron Electron Nucleus Energy levels Mass number Electromagnetic force Strong nuclear force

The force that holds the atom together is called Proton Neutron Electron Nucleus Energy levels Mass number Electromagnetic force Strong nuclear force

The total number of protons and neutrons in the nucleus of an atom Electron Nucleus Energy levels Mass number Electromagnetic force

C-12 How many protons? How many electrons? How many neutrons? Draw a atomic model for this element? C-12

C 14 6 How many protons? How many electrons? How many neutrons? Draw a atomic model for this element? 14 C 6

Li 7 3 How many protons? How many electrons? How many neutrons? Draw a atomic model for this element? 7 Li 3

N 14 How many protons? How many electrons? How many neutrons? Draw a atomic model for this element? 14 N

Na-23 How many protons? How many electrons? How many neutrons? Draw a atomic model for this element? Na-23

How many protons? How many neutrons? 238 U

Be-9 atomic number? 1 2 3 4 5 6 11

Be-9 number of protons? 1 2 3 4 5 6 11

Be-9 number of electrons? 1 2 3 4 5 6 11

Be-9 number of neutrons? 1 2 3 4 5 6 11

Be-9 number of energy levels? 1 2 3 4 5 6 11

14Si valence electrons? 1 2 3 4 5 6 11

7N valence electrons? 1 2 3 4 5 6 11

Be-9 number of electrons in the first energy level? 1 2 3 4 5 6 11

17Cl number of electrons in the first energy level? 2 3 4 5 6 11

Complete the energy levels … 7 NITROGEN # of Protons? # electrons? # e’ in 1st orbital? # e; in 2nd orbital? # of valence e’ ? 7 2 5 5

Who discovered the electron? Electrons in the outer energy are called? 3. The columns in the periodic table are called JJ Thomson Valence electrons Groups

NEED YOUR PERIODIC TABLE FOR THIS ONE Find SULFUR (atomic # 16) How many valence electrons does it have? Which orbital is being filled? 6 3rd

Element or compound?? Hydrochloric acid HCl 2. What element is most closely related to Bromine? 3. What does the group # tell us? Compound Fluorine / Chlorine The # of valence electrons

# of the energy level being filled 1. Who did the gold-foil experiment? 2. Who stated that elements are made of atoms? 3. What does the period # tell us? 4. Who created the term “atomos”? Rutherford Dalton # of the energy level being filled Democritus

Which are the metals? Nonmetals? B A B C A