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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.