9.1 Organizing the Elements

Atoms and the Periodic Table- Course 3

What Did Mendeleev Discover?

Dmitri Mendeleev studied the properties of the 63 known elements in an attempt to organize them. He used an element’s melting point, density, color, and atomic mass. Atomic mass is the average mass of all of the isotopes of that element. Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass. He found that the properties of the elements repeated.

Mendeleev’s Periodic TableIn his periodic table, Mendeleev left blank spaces. He predicted that the blank spaces would be filled by elements that had not yet been discovered. He even correctly predicted the properties of those new elements.

Organizing the Elements

Organizing the ElementsApply It !

A pattern can be described as a recognizable design or relationship. Mendeleev organized elements using patterns in their properties. From these patterns, he was able to make predictions about unknown elements. See if you can do the same with a group of buttons.

1.Classify- Identify a pattern that helps you sort the buttons into two or more groups. Write the letters of the buttons in each group, then tell the pattern you used.__________________________________________________________________________________________

2. Predict- If you were to add another button to each group in Step 1, what would each of the new buttons look like? ______________________________________________________________________________________

Assess Your Understanding

1a. Review In what order did Mendeleev arrange the elements in his periodic table?

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b. Understand Scientific Investigations Why do you think that looking for patterns can be useful when doing scientific investigations?

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c. Recognize Groupings How could Mendeleev predict the properties of elements that had not yet been discovered?

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d. Pose Questions What is one thing you would like to know about how the periodic table that is used today differs from Mendeleev’s?

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What Information Does the Periodic Table Contain?

To understand the periodic table, you need to know something about atoms. Atoms are made of protons, neutrons, and electrons. Protons and neutrons together make up the nucleus.

The Parts Of An Atom

Nucleus- At the center of an atom. It contains the Protons and Neutrons.

Protons- Positively charged particles.

Neutrons- Particles with no charge.

Electrons- Negatively charged particles.

Organizing the Elements

Structure of an AtomName one thing you have learned about each labeled part of the atom.

Reading The Periodic Table

Every atom of the same element has the same number of protons, called the atomic number. The number of protons also determines the chemical properties of an element. As a result, modern periodic tables are arranged in order of increasing atomic number.

Atomic Number = # of Protons

# of Protons = # of Electrons

Element Symbol = 1 or 2 letters

Atomic Mass = # of Protons + Neutrons

PotassiumPotassium has an atomic number of 19 and an atomic mass of 39.098 amu. Bananas are rich in potassium.

Organizing the Elements

Apply It! SiliconThe entry for silicon (Si) in the periodic table looks like this.

1.The Atomic Number of silicon

Is ______________________

2.Predict – Without looking at the periodic table, do you think that any other element has the same atomic number as silicon? Explain.______________________________________

______________________________________

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Organizing the Elements

The Periodic TableThe periodic table is one of the most valuable tools to a chemist.

Find the element identified by the atomic number 25 on the periodic table. Use the information to fill in the blanks below.

Name of element_______________Chemical symbol_______________Atomic Mass_______________

Organizing the Elements

Assess Your Understanding

2a. Compare and Contrast- Describe two differences between Mendeleev’s periodic table and the modern periodic table.

____________________________________________________________________________________________________________________________________________________________________________________________________b. Interpret Tables- An atom of which element has 47 protons in its nucleus?

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How is the Periodic Table Useful?

The periodic table is made up of :

• rows called periods

• columns called groups or families.

• There are seven periods and 18 groups.

• The properties of an element can be predicted from its location in the periodic table.

• Metals are shown on the left of the table

• Nonmetals are shown on the right.

• Metalloids are located between the metals and nonmetals.

This pattern is repeated in each period and accounts for the fact that elements in the same group have similar characteristics.

Element Scramble

Organizing the Elements

Elements of Period 3The properties of the Period 3 elements change as you move across the period. Which of these are Metal? Metalloid? Nonmetal?

Classify Use 3 different colors to fill in the key below. Then color in each element in period 3 according to your key.

PERIODS PARADE ACROSS

Organizing the Elements

KeyMetalMetalloidNon Metal

Elements of Group 10The elements of Group 10 include •nickel (Ni)•palladium (Pd)•platinum (Pt•darmstadtium (Ds).

GROUPS GO DOWN

Organizing the Elements

Assess Your Understanding

3a. Name The rows in the periodic table are called __________.

The columns in the periodic table are called ______________.

b. Recognize What do elements in the same group in the periodic table have in common?

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c. Predict Use the periodic table to name 2 elements that you would expect to have properties very much like those of calcium (Ca). ______________________________________________________________________________________________________