Periodicity and the Quantum Electron Model

Chapters 5 and 6

Part A – THE BASICS OF PERIODIC TABLE

Target 1 – Explain how elements are arranged on the periodic table based on similarities.

A. Elements are arranged on the periodic table based on similarities.

B. At a grocery store, you find food items located around the store based on similarities. Fruits are with fruits, and meats are with meats – and so forth.

C. So what about atoms? How can they be

grouped based on similarities?

D. As elements were discovered over the centuries, chemists began to notice certain properties.

E. For example, when Chlorine, Bromine, and Iodine were discovered, scientists noticed that all 3 of these elements react easily with metals.

F. Notice that chlorine, bromine, and iodine are all in group 7. (just like a grocery store)

G. After all of the major discoveries, it was decided that the order of the periodic table would be based on the atomic number (protons).

Target 2 – Identify Groups and Periods on the Periodic

Table.A. The periodic table is based on groups and

periods.

B. Groups run vertical. For example, Group 1 contains Hydrogen, Lithium, Sodium, Potassium…

1. Elements in the same group will have the

same number of valence electrons.

2. Elements that are in the same group will have similar properties.

3. Example 1, the elements in group 1 will all explode when placed in water.

4. Example 2, the elements in group 7 will react easily with metals.

C. Periods run horizontal. For example, Period 2 contains Lithium , Beryllium, Boron, Carbon…

1. Elements in the same period will have the same number of energy levels.

2. Elements in the same period will NOT have similar properties

questions

Target 3 – Identify the 3 main classes of elements on the

periodic tableA. There are 3 main classes of elements on

the periodic table.

1. Metals

2. Non-Metals

3. Metalloids

Target 4 – List the properties of each class of elements on the

periodic table.

A. Metals

1. Good conductor heat and electricity

2. Shiny luster when cleaned

3. Solid at room temperature

4. Malleable and ductile

B. Non-metals

1. Poor conductor of heat and electricity

2. If not a gas, they usually have a dull luster (not shiny)

3. Usually a gas at room temperature

4. Brittle

C. Metalloids

1. Metalloids have properties similar to both metals and non-metals.

2. Sometimes they behave like a metal, sometimes like a non-metal.

Target 5 – Identify the Families on the Periodic Table (pg

162)A. The periodic table can be broken down

into 10 families.

B. Elements found in the same family will have similar properties.

C. Insert families periodic table

Target 6 - Identify the 4 blocks on the periodic table

The periodic table can be divided up into 4 blocks – based on electron configurations.

questions – 2min 37.2 secs

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Part B – TRENDS ON THE PERIODIC TABLE

Target 7 – Define the word “Trend” and give examples.

A. A trend is an occurrence in nature that usually happens, but not always; general tendency or direction.

B. Trend 1: Learning occurs more in classrooms where there is a lot of order. (positive relationship)

C. Trend 2: Weight loss occurs more when people go out and exercise. (inverse relationship)

List some other trends

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Target 8 – Define diatomic and explain how the radius (size) of an element can

be calculated.A. It is difficult to measure the size of an atom because the

outer boundary is made of electrons flying around the nucleus.

B. The current theory of atoms is that they are spherical in shape.

C. Some atoms are diatomic – which means two atoms of the same element bond together.

D. There are seven common diatomic elements. H2, O2, N2 , F2, Cl2, Br2, I2

E. The diagram below lists the radii of the seven common diatomic elements

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F. Because two atoms of the same element must be the same size, the size of an atom can be calculated by knowing the distance between the two nuclei.

G. The size of an atom is measured by its radius.

H. Atomic radius is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined.

I. The atomic radius is measured in

picometers(pm)

J. One picometer is one trillionth of a meter (10-12 meters or 0.00000000001 meters)

K. For example, the distance between the nuclei in an iodine molecule (I2) is 280 pm, therefore the radius of one iodine atom is 140 pm.

notes – radius of 2 attached circles

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L. If you know the radius of a sphere, you can

calculate the volume(size).M. Remember from earlier that the volume of

a sphere can be calculated with this formula 4/3πr3

N. The volume of each element is not important in this class – you may choose to calculate that on your own time.

O. The important thing to realize is that the radius of an atom is proportional to its size (volume).

questions

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Target 9 – Explain the trends of the atomic radius of various atoms

on the periodic table. A. Moving down the periodic table

1. As you move down vertically on the periodic table in a group, the atomic radius INCREASES.

2. Why? As you go down the periodic table, the number of energy levels increase.

3. Example 1: Potassium has 4 energy levels and Sodium has 3 energy levels – therefore potassium is a larger atom than sodium.

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B. Moving across the periodic table

1. As you move across a period from left to right, the atomic radius DECREASES.

2. Why? As you go across the periodic table, the atomic number increases by one proton.

3. Remember that one proton has a charge of +1…As the charge of the nucleus increases as you move across a period, it creates a stronger pull on the electrons.

4. This stronger pull of electrons draws them in closer to the nucleus, and therefore causes overall size of the atom to decrease.

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Target 10 – Define ion and explain how they are formed.

We learned earlier that the atomic number will tell you how many electrons an atom will contain.

This is true in some cases.

In most cases, elements will not have the same amount of protons as electrons.

Therefore, the atomic number does not give you an accurate count of electrons.

A.

Sometimes atoms gain electrons and sometimes atoms lose electrons.

Ion – an atom with a different number of protons and electrons – resulting in an overall positive or negative charge.

In other words, an atom with a charge is called an “ion” not an “atom”

When an atom loses electrons, it becomes positively charged – this is called a cation

When an atom gains electrons, it becomes negatively charged – this is called an anion.

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notes cation/anion

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Target 11 - Explain how ions can be different sizes than their

component atoms.Again - Atoms that have a charge (positive or

negative) are called ions.Ions will be of a different size than it’s component

atom – why is this?Example 1, when sodium loses an electron, it has

more protons than electrons. Therefore the overall electron cloud is pulled in closer to the nucleus – thus the size of the atom decreases. Illustrated below.

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notes - potassium •

Example 2: When a chlorine atom gains an electron, it has more electrons than protons. Therefore the overall electron cloud is released – just a little, from the nucleus – thus the size of the atom increases. Illustrated below.

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notes fluorine

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E. Cation Trend – Cations are smaller than their component atoms. For example, a potassium cation is smaller than a potassium atom.

F. Anion Trend – Anions are larger than their component atoms. For example, a fluorine anion is larger than a fluorine atom.

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Target 12 – Explain how ionization energy can create an ion.

A. Electrons are not always limited to their proper energy level.

B. If you add the appropriate amount of energy, an electron can jump to a higher energy level.

C. Sometimes, if enough energy is added, electrons can completely jump from the atom – creating an ion – this is called ionization.

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D. The energy required to remove an electron

from an atom is called “ionization energy.”

E. There are several electrons in most atoms, therefore, we must be more specific.

F. The energy required to remove the first electron from an atom is called “first ionization energy.”

G. The energy required to remove the second electron from and atom is called “second ionization energy.” Third ionizations also exist (and so forth)

H. Typically, the first ionization is the easiest

– requiring the least amount of energy.

I. The second and third ionization energies require more energy.

J. The unit for this measurement is KiloJoule per Mole (KJ/mol) (The mole explanation will come later)

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Target 13 - Explain the trends of ionization energy of various atoms

on the periodic table.A. As you move down a group, the ionization

energy decreases.

B. Why? As you move down a group, the atomic size increases – this creates a lot of space between the nucleus and the electrons. Therefore, it is easier to remove an electron.

C. As you move across a period – from left to right, the ionization energy increases.

D. Why? As you move across a period – from left to right – the atomic size decreases. This creates less space between the nucleus and the electrons. Therefore it is harder to remove an electron.

notes

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Target 14 – Define Electronegativity and explain the trends of electronegativity on the periodic table.

A. Electronegativity – the ability of an atom to attract electrons when the atom is bonded in a compound.

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Example of water and carbon dioxide

B. Electronegativity is measured in units called “Paulings” named after the inventor of the concept Linus Pauling.

C. The range of Paulings 0 – 4.

D. The element with the lowest electronegativity is Cesium (0.7 Paulings) and the element with the highest electronegativity is Fluorine (4.0 Paulings).

E. As you move down the periodic table, elecronegativity decreases.

F. As you move across the periodic table from left to right, electronegativity increases.

G. Learning why requires more detailed understanding and is not part of this course – just know the trend.

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