unit 2/b: chemical interactions

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Unit 2/B: Chemical Interactions

Chapter 5: Atomic Structure and the Periodic Table

Chapter 6: Chemical Bonds and Compounds

Chapter 7: Chemical ReactionsChapter 8: Solutions

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Chapter 5: Atomic Structure and the Periodic Table

5.1 Atoms are the smallest form of elements5.2 Elements make up the periodic table

5.3 The periodic table is a map of the elements

A substance’s atomic structure determines its physical and chemical

properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.2 Elements make up the periodic table

Before, you learned:•Atoms have a structure•Every element is made from a different type of atom

Now, you will learn:•How the periodic table is organized•How properties of elements are shown by the periodic table

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Warm-up questions

• The atomic number of an atom is the number of protons and neutrons in the nucleus

• Atomic mass number• Isotopes are atoms of the same element, but with

a different number of neutrons• True• When an atom gives up an electron, it becomes an

ion with a negative charge• positive

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

1. Complete the table below, considering 'normal' atoms only (not ions or isotopes).

Table 1. Characteristics of Some Elements

2. What is the atomic weight of the normal oxygen atom? Of the normal argon atom?

3. What is the atomic weight of a hydrogen atom? Of a hydrogen ion?

Element # Electrons # Protons # Neutrons

hydrogen 1

helium 2 2

sodium 11 11

chlorine 17

argon 18 18

carbon 6

nitrogen 7

oxygen 8

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Numbers and Mass Numbers

• All atoms are composed of the same particles…– Different numbers of protons in the nucleus

• Atomic number = # protons in the nucleus• Atomic mass number = # protons + # neutrons

– Same elements have same # protons but not always the same # neutrons, so may have different atomic masses

– Ex: Chlorine atoms have 17 protons, some have 18 neutrons, some have 20 neutrons = Chlorine isotopes

– Isotopes: atoms of the same element that have a different number of neutrons• Chlorine-35, Chlorine-37

– # protons? # neutrons?

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Formation of Positive Ions

• If the atoms loses one electron, the charges are no longer balanced: one more proton than electrons

• Size is different: fewer electrons, less repulsion• Lose one electron: X+, lose two electrons: X2+ Ex: Na+, Ca2+

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Formation of Negative Ions

• If the atoms gain one electron, the charges are no longer balanced: one less proton than electrons

• Size is different: more electrons, more repulsion• Gain one electron: X-, gain two electrons: X2- Ex: Cl-, O2-

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.2 Elements make up the periodic table

• Elements can be organized by similarities– Masses• Can find the mass of a very large number of atoms of a

certain elements and infer the mass of a single one of them• Can vary for an element: isotopes• “atomic mass” is actually the average mass of all the

element’s isotopes

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Mendeleev’s Periodic Table• Russian chemist, Dmitri Mendeleev

– 1860’s – how to organize the elements based on physical and chemical properties?

– He made cards that contained atomic mass and properties• He looked for a relationship between the properties and atomic mass

– He created a chart:• Rows: elements showing similar chemical properties• Atomic mass increased by moving down each vertical column

– 1869 – first periodic table – “periodic” – shows a periodic, or repeating, pattern of properties of the elements

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Predicting New Elements

• Mendeleev left empty spaces on the table where no known elements fit the pattern– Predicted new elements fitting the spaces would

eventually be discovered – described their properties!

– Six years later the “?” after aluminum (Al) was discovered: “gallium

– In the next 20 years, two others were discovered

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

The periodic table organizes the atoms of the elements by properties and atomic number

• New table: elements with similar properties are now found in columns, not rows…and atoms are now arranged by atomic number, not mass

• How to read the periodic table?

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

How to Read the Periodic Table?

1. The number at the top is the atomic number = # protons in the nucleus

2. Chemical symbol - one or two letters; temporary symbols for not-yet named elements have three-letter symbols

3. Name of element4. number at bottom is the

“average atomic mass” of all the isotopes of the elements

Color of symbol is the state of matter at room temperature

Color of background color of box indicates whether metal, nonmetal, or metalloid (5.3)

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Groups and Periods• Elements in a vertical column show similarities in their

chemical and physical properties– Known as a group– Labeled by a number at the top of the column– Sometimes a group is called a family of elements because they

seem to be related– Ex: Group 17 – “Halogen” group

• Tend to combine easily with other elements and compounds, especially elements in Gropus 1 and 2

• Different physical properties– At room temperatures: Flourine and chlorine are gases, bromine is a liquid,

iodine and astatine are solids

– Ex: Group 1 – • Some metals – lithium, sodium, potassium, for example – react

violently with water

• Horizontal row in the periodic table = period– Properties of elements change in a predictable way from one

end of a period to the other– Ex: Period 3 = elements on far left are metals, far right are

nonmetals

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Trends in the Periodic Table• An element’s position in the table can give information about that element• Ions form by an atom gaining or losing electrons

– Atoms of elements on the left side of the table form positive ions• Group 1 atoms lose an electron to form ions 1+• Group 2 atoms lose two electrons to form ions 2+• Group 18 atoms normally do not form ions• Group 17 often form ions 1-• Group 16 often form ions 2-• Groups 3 through 12 all form positive ions with varying charges

• Sizes of atoms vary across periods and within groups– Size affects how the atom will react with another atom

• Densities follow a pattern– Generally increases from top of a group to the bottom– Within a period, elements at the left and right sides are the least dense, the middle are the most

dense• Ex: Osmium (Os) has the highest known density

• Trends are a valuable tool, though exact size or density of an atom cannot be predicted exactly

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties