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Edexcel GCSE Chemistry Periodic table structure

Periodic table structure

This page covers the following topics:

1. Ordering in periodic table
2. Groups in periodic table
3. Rows in periodic table
4. Metals and nonmetals

In 1869, Russian scientist Mendeleev designed the periodic table that is still used today. The elements were ordered by their atomic number and grouped by their physiochemical properties.

Periodic table allowed scientists to predict how theoretical undiscovered elements would act and over the years gaps that previously existed in the periodic table have been filled in. The periodic table got its name from the periods (rows) in the table which show common trends in atomic structure and properties that are similar for the elements in the same columns, called groups.

Ordering in periodic table

There are specific names used for some groups of the periodic table:
group 0/8 (18) β†’ noble gases
group 1 β†’ alkali metals
group 7 (17) β†’ halogens

Elements in the same group have similar properties since they have the same number of electrons in their outer shell. For groups 1-2 and 3-8 it is the same as the group number. For example, phosphorus has 5 electrons in its outer shell. If you use a periodic table with 1-18 group numbers, you should convert groups 13-18 to 3-8 respectively as the aforementioned rule doesn’t necessarily apply for the groups 3-12.

As you go down a group, the elements get bigger as they gain additional shells of electrons.

Groups in periodic table

Rows in the periodic table are called periods, they are numbered and represent how many shells of electrons an element has. Each period of elements has elements with the same number of electron shells. For example, period 1 elements have 1 shell of electrons and period 5 elements have 5 shells of electrons.

As you move towards the right across a period, the atomic number and nuclear charge gets bigger. This causes a greater attraction between the nucleus and the electrons, pulling them closer to each other. Thus, the size of an atom gets smaller. The number of shells is more important than the position within a period while considering the size of an atom.

Rows in periodic table

Where an element is found in the periodic table can tell you a lot about its physical and chemical properties. Most elements are metals except for the top right corner of the periodic table and hydrogen. In between metals and nonmetals we can find metaloids that have properties similar to both metals and non-metals.

Since the group an element is in indicates how many electrons are in the outer shell, it can be used to determine the ionic charge. Metals usually form positive ions with the charge of their group number and a plus (+). Nonmetals usually form negative charges with their charge being their group number minus 8.

Metals and nonmetals

1

Which element has largest atoms of the following - lithium, magnesium or scandium?

Which element has largest atoms of the following - lithium, magnesium or scandium?

2

Would sodium behave in chemical reactions more like potassium or magnesium? Explain your answer.

Would sodium behave in chemical reactions more like potassium or magnesium? Explain your answer.

3

Explain why boron isn’t considered a nonmetal.

Explain why boron isn’t considered a nonmetal.

4

What is the most probable charge a phosphorus ion would have?

What is the most probable charge a phosphorus ion would have?

5

Catherine predicts that there could be an undiscovered element with atomic number 120. What group in the periodic table would this element belong to?

Catherine predicts that there could be an undiscovered element with atomic number 120. What group in the periodic table would this element belong to?

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