The Periodic Table is an arrangement of
chemical elements ordered by atomic number.
It was designed by Dmitri Mendeleyev as a
way of presenting
all the elements to show their similarities
and differences.
Every element is listed on the Periodic Table
and is contained in its own box.
The elements are arranged in increasing order
of
atomic number as you go from left to right
across the table.
The horizontal rows are called "periods."
To which of the following is the atomic number
equal?
Choose the correct answer.
The correct answer is A.
The number of protons.
The atomic number is equal to the number of
protons.
Many elements have similar properties which
make them behave the same way.
They are arranged in vertical columns, called
"groups."
The groups are titled using numbers and
are labeled across the top of the table.
For instance, in the far left column,
all the elements in that column are very similar.
That means we know lithium, with the symbol
Li,
sodium with the symbol Na, and potassium,
with the symbol K,
are very similar because they are all in the
same column.
Looking in Group 16 we see oxygen and sulfur.
That means that oxygen and sulfur are very
similar to each other.
Elements on the Periodic Table can also be
divided into categories:
metals, non-metals, and metalloids.
Metals are on the left side of the table.
Common examples of metals are gold, silver,
and iron.
Other examples that many people do not know
are metals are calcium,
potassium, and sodium.
Non-metals are found on the right side of
the table.
Examples of non-metals are oxygen, carbon,
and nitrogen.
The elements located between metals and
non-metals on the Periodic Table are called
"metalloids,"
and are found in a stair-step or
jagged pattern towards the right side of the
table.
Metalloids can, in some ways, act as metals
and,
in other ways, as non-metals.
Examples of metalloids are silicon and arsenic.
Calcium is an element in Group 2 of the Periodic
Table.
Which other elements have similar properties
to calcium?
The correct answer is B. Magnesium.
Because they are in the same column,
we know that they have similar properties.
There is a lot of information about each element
on the Periodic Table,
and it may seem very cluttered and difficult
to read.
The information presented for each element
is
information we discussed in section 1:
element name,
element symbol,
atomic number,
atomic mass,
and mass number.
Let us look at the element beryllium for an
example,
and the information presented.
Two of the items displayed in the box are
the element name and symbol.
The atomic number is displayed above the element
symbol,
and as we know from section 1, is the number
of protons the element has.
Beryllium has an atomic number of four; therefore
we know it has four protons.
The atomic mass is listed below the element
name and
is the average mass of the protons and neutrons.
