Unit C: Exploring Matter
Chapter 6: Elements and the Periodic Table
6.1: Atoms and Elements
pg. 210
Key Concepts:
1. Elements cannot be broken into simpler substances.
2. Elements of the same column (group) of the periodic
table have similar properties.
3. Atoms consist of protons and neutrons in the central core
surrounded by electrons.
Parts of the Atom
Proton: a positively charged particle in an atom.
Neutron: a particle in an atom that has no electrical charge.
Electron: is a negatively charged particle found in an orbit
outside the nucleus of an atom.
An atom contains three kinds of sub atomic particles. The
protons (positively charged) and the Neutrons (neutral
charge) are found within the nucleus of the atoms. The
Electrons (negatively charged) are found orbiting the
nucleus of the atom.
The mass of the atom is found within the nucleus, each of
the protons and neutrons have the same mass.
Electrons have very little mass, and are found orbiting the
nucleus, but also create the volume of the atom.
An atom has a neutral charge. Therefore there are an equal
number of protons to electrons, creating a balance. One
positively charged proton for each negatively charged
electron.
Table 1: Particles in an Atom.
Particle
Name
Proton
Neutron
Electron
Charge
Location
Symbol
Positive +
No charge
Negative -
Nucleus
Nucleus
Orbit
p+
n0
e-
Figure 1: This model of a fluorine atom shows that it has 9 protons (9 p+), 9 electrons
(blue dots), and 10 neutrons (10 no). There are 2 electrons (2 e-) in the first orbit and 7
electrons in the second orbit (7 e-).
Electron Orbits (Electron Energy Shells)
Electrons are found in the orbits (Electron shells) outside
the nucleus. The first orbit (shell) can only contain 2
electrons. The second orbit (shell) can contain 8 electrons,
a long with the third orbit.
The Importance of Organizations
Organizing the Elements: On the Periodic Table
Element: is a pure substance that cannot be broken down
into simpler substances, either physically or chemically.
Periodic Table: the table that lists all the known elements
in rows and columns based on patterns of similar properties.
All matter is made up of elements. Gold, copper, and
oxygen are examples of elements. Each element is made up
of only one type of particle or atom.
Gold and copper have different properties because they are
made up of different types of atoms. Gold is made up of
gold atoms and copper is made up of copper atoms.
Scientist record data in tables, the elements are recorded in
a periodic table, which organizes and arranges the elements
with similar properties in groups or families.
The Modern Periodic Table
Atomic Number: is the number of protons in an atom of an
element; each element has a different atomic number.
Period: is a horizontal row in the periodic table of elements.
Group or Chemical Family: is a vertical column in the
periodic table of elements.
The elements found in the periodic table are arranged in
order of the number of protons they contain in their nucleus.
The number of protons for each element is known as the
Atomic Number. Each element has its own atomic number.
Figure 4: The atomic number is at the top left-hand
corner of each element on the periodic table.
- Each element in the periodic table has its own box. In the
box is the element’s chemical symbol, name, and atomic
number.
- The first letter of every chemical symbol is a capital letter.
(N for Nitrogen) If there is a second letter, it is lowercase.
(Ne for Neon)
- Each row of the periodic table is called a Period. The
properties of the elements that are in the same period can
be very different.
- The elements are also placed in columns according to how
their electrons are arranged. Each column in the periodic
table is called a group or chemical family. Elements in the
same group have the same properties. Within each group,
all atoms have the same number of electrons in their outer
most orbits, or electron shells. (Valence Electrons)
- Most elements are either metals (blue boxes) or nonmetals (pink boxes). They are separated by a dark line that
looks like a staircase. Hydrogen is the only exception.
Elements along the staircase have properties in between
those of metals and non-metals. These elements are called
metalloids (green boxes).
Figure 3: The elements of the periodic table are arranged in rows (also called periods)
and columns. Each group of elements has similar properties.
Chemical Families
The structure of the atoms explains why elements have
similarities and difference.
Group 1:
Alkali metals, consists of elements below hydrogen, in the
first column of the periodic table. Lithium (Li), sodium
(Na), potassium (K) and other elements have only one
electron found in their outer electron shell or orbit.
They will react the same, during chemical reactions.
Group 2:
Elements in group 2 are called Alkaline Earth Metals.
Beryllium (Be), Magnesium (Mg), Calcium (Ca),
Strontium (Sr), Barium (Ba), and Radium (Ra), all contain
two electrons in their outer electron shells or orbits.
They will react the same, during chemical reactions.
Periodic Trends
Elements in the same group or family share some chemical
and physical properties and also in their reactivity.
Group 1 is more reactive then group 2.
On the right side of the periodic table, group 17 (Halogens)
is more reactive then group 16. Group 16 is more reactive
then group 15.
Figure 5: These elements react in a similar way because
each atom has one electron in its outermost electron
orbit.
Check Your Learning:
Questions 1 – 11, pg. 217
Wrap Up:
- Protons and neutrons are found in the nucleus of the atom.
Electrons orbit the nucleus.
- Protons are positively charged and have about the same
mass as neutrons, which have no charge. Electrons are
negatively charged and have very little mass compared to
protons and neutrons.
- The numbers of protons and electrons in an atom are
equal. The positive and negative charges cancel each other
out, giving the atom a neutral charge.
- Elements cannot be broken down into simpler substances.
- The elements in the periodic table are in order by
increasing atomic number.
- Elements in the same group have similar properties.