Unit 2/B: Chemical Interactions
Chapter 5: Atomic Structure and the
Periodic Table
Chapter 6: Chemical Bonds and
Compounds
Chapter 7: Chemical Reactions
Chapter 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
A substance’s atomic structure
determines its physical and chemical
properties
5.1 Atoms are the smallest form of elements
5.2 Elements make up the periodic table
5.3 The periodic table is a map of the
elements
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
Element
# Electrons
hydrogen
# Protons
1
helium
2
2
sodium
11
11
chlorine
argon
# Neutrons
17
18
18
carbon
6
nitrogen
7
oxygen
8
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?
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: X2Ex: Cl-, O2Atomic 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 element
4. 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
Atomic Structure and the Periodic Tableindicates
-A
whether metal,
substance’s atomic structure determines its
physical and chemical properties nonmetal, or metalloid (5.3)
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 =Atomic
elements
on far left are metals, far
Structure and the Periodic Table - A
right are nonmetals
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 1Group 16 often form ions 2Groups 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
Atomic Structure and the Periodic Table - A
substance’s atomic structure determines its
physical and chemical properties