Atomic Structure

Atoms are the building blocks of matter, and the smallest unit of an

element.

Warm Up

Illustrate and label the following atomic models:

1.Dalton

2.Thompson

3.Rutherford

4.Bohr

Homework

• 4.1 pg 91 1-3

• 4.2 pg 97 6-8

• Pp pg99 11-13

• Pp pg 101 14

• 4.3 pg 104 18-20

• 4.4 pg 107 23-25

Warm Up

1. Name three things that a block on the periodic table tells you.

2. Uranium 235 is element 92. How many neutrons does uranium have?

3. What is an a.m.u.?

4. How much do protons, neutrons and electrons weigh in a.m.u.’s, respectively?

5. The atomic mass of helium is 4.003. Why?

Warm Up

1. Define an alpha particle.

2. Define a beta particle.

3. Define a gamma particle.

4. What is radiation?

5. What is radioactive half-life?

Warm Up

1. What are the 3 parts of an atom and what are the charges associated with each?

2. Name the following elements: Be, Zr, Ge, Ni, Sc, Y, K, Na, F and Ne.

3. Give the symbols for the following elements: iron, magnesium, chromium, gallium, helium, gold, silver, copper, manganese and mercury.

4. Give the atomic number for the following: hydrogen, boron, aluminum, titanium, niobium, zinc, molybdenum, platinum, vanadium and strontium.

Warm Up

1. What is the average atomic mass of the following: Au, Ag, Ni, C, Na and Cr.

2. How is average atomic mass determined

3. Define the term isotope.

4. How do isotopes relate to average atomic mass.

5. What are valence electrons?

Warm Up

1. According to the 2n2 rule, what are the maximum number of electrons that will fit in the 5th orbit of an atom?

2. According to the 2n2 rule, what are the maximum number of electrons that will fit in the 6th orbit of an atom?

3. According to the 2n2 rule, what are the maximum number of electrons that will fit in the 3rd orbit of an atom?

4. Draw electron configurations for the following atoms: Na, Al, P, Ar and Si.

Warm Up

1. The element deuterium has an atomic number of 1 and has 1 neutron. What is it’s mass, symbol and number of electrons?

2. Chlorine has a mass of 37 amu’s. What is its symbol, atomic number and number of neutrons?

3. An unknown element has an atomic number of 12 and a mass of 25 amu’s. What is it? How many neutrons does it have?

4. An unknown element has 92 electrons and a mass of 238. What is its name, atomic number and number of neutrons?

5. Draw an electron configuration for the following elements: potassium, boron, fluorine and vanadium.

What does the periodic table tell you about an atom?

• Symbol tells the name of the element. Ex. (Ne is Neon)

• Atomic number = the # of protons in the nucleus. (and the number of electrons in a balanced or neutrally charged atom)

• Average Atomic mass = the weighted average one atom and its Isotopes.

• Atomic Mass or Mass # = how many protons and neutrons are in the nucleus.

Inside the center of an Atom

• Nucleus – the dense center of an atom.• Proton- the positive charged subatomic particle,

located in the nucleus. (determines the atomic number of an element)

• Neutron- the neutrally charged subatomic particle in side the nucleus.

• Isotope-an atom who’s # if neutrons is different or not equal to the number of protons.

• Atoms can exist as many different isotopes. (ex Carbon-12, Carbon-14)

Outside the nucleus of an atom

• Electron- the negatively charged subatomic particle of an atom.

• Located in clouds that exist in various energy levels or shells.

• General rule is n1=2, n2=8, n3=18, n4=32 but there are exceptions. Most typical exceptions are electron configurations of transition metals.

Significance of Valence Shells

• Valence Shell- the outer most energy level. (energy levels increase from the inside out)

• The # of electrons in the valence shells determine an atoms ability to react with other atoms.

• Electrons can be gained or lost from valence shells, forming ions.

Ions

• Ion-an atom that has gained or lost an electron.• When an atom loses an electron from its

Valence shell, the result is a positively charged ion because the # of electrons is less than the # of electrons.

• When an atom gains an electron in its Valence shell, the result is a Negative charged ion because the # of electrons is greater than the # of protons.

Element

• A substance that cannot be broken down into smaller substance.

• Elements are arranged in a certain order based on atomic number on the Periodic Table.

Periodic Tablehelps determine electron arrangement

• Periodic Law states that the chemical and physical properties of elements change periodically with the atomic # of elements.

• Periods – a horizontal row of elements. Indicates how many energy levels the atoms in that row contain. (how many orbital shells)

• Groups (family)- a vertical column of elements in the periodic table. Indicates how many electrons are in the valence shell. ***(The transition metals are the exception and do have different numbers of electrons in their valence shells)

Elements are classified into 3 groups

• Metals – an element that is shiny and conducts heat and electricity well.

• Metalloids (semiconductors) – conducts electric current better than a non metal (insulator), but not as well as a metal (conductor)

• Non metals – do not conduct heat or electricity.

Metals

• Alkali metal – any element in Group 1 of the periodic table.

• Alkaline Earth Metal- any element in Group 2 of the periodic table.

• Transition Metal – any element in Groups 3-12 of the periodic table.

Alkali Metals

• Found in Group 1• Have 1 valence electron – this electron can

easily be removed to form a positive ion, and is the reason elements in this group are highly reactive with other atoms. (especially elements in Group 7)

• Are typically soft and shiny• React violently with water.• Typically not found in nature as elements

because they are so reative.

Alkaline Earth Metals

• Found in group 2• Have 2 valence electrons that can be lost,

which causes them to form +2 ions.• Not as reactive as alkali metals, but still

highly reactive often forming compounds with atoms of other elements.

• Silvery white in color• High melting points• Low densities

Transition Metals

• Found in Groups 3-12• Have a complex arrangement of electrons.• Only somewhat reactive, but are still capable. It

takes more energy for transition metals to gain and lose their valence electrons.

• Can lose up to 4 electrons.• Are malleable – can be stretched and shaped.• Are often shiny – or lustrious.

Metalloids - Semiconductor

• Exist in diagonal a diagonal cluster from group 13 – 17.

• Only 6 elements- boron, silicon, germaninum, arsenic, antimony, and tellurium

• Able to conduct heat and electricity under certain

Non-metals

• Halogens - Group 17 – Very reactive

• Contain 7 electrons in valence shell.

• Tendency to gain an electron.

• Like to bond with Alkali metals.

• Smell bad.

• Noble gases – Group 18, “Inert gases”.

• Exist as single atoms.• Very rarely form

molecules.• 8 valence electrons

that saturate the valence shell. (fill up to capacity)

Assessment1. Classify the following elements.2. a. Iron, Fe b. Strontium, Sr c. potassium, d. Platinum,

Pt3. Predict whether Cesium form Cs+ or Cs- ions.4. Predict the charge of a beryllium ion.5. Which element is more reactive? Lithium, Li or Beryllium, Be?

Why?6. How many neutrons are in the element with atomic #18? Name

this element._________7. What is the mass number of this element?____8. What family does this element belong to?___ Which Period?___9. Is this element very reactive?___ Why?10. If this element were to lose 2 electrons, what would be the net

ionic charge?