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The Periodic Table

The Periodic Table is the arrangement of elements in tabular form based on atomic numbers and electronic configurations. The elements are presented in order of increasing atomic number (number of protons in the nucleus) in a table with 9 rows and 18 columns (which are also called groups). Although there are 18 groups in total, there are only 8 main groups based on the number of valence electrons. So if two elements had the same number of main electron shells, then they would be placed in the same row in the periodic table. If two elements had the same number of valence electrons, then they would be placed in the same group. If an element had an atomic number which was higher than an element in the same row, it would be placed to the right of it in the periodic table as it is organized in ascending order. For example, the elements carbon and nitrogen both have 2 main electron shells – this is why they are both placed in the second row of the periodic table. Phosphorus on the other hand has 3 main electron shells, but has five valence electrons just like nitrogen – this is why it is placed just underneath nitrogen. Thus, understanding the rules and complexities of the periodic table may be useful for chemists in predicting elemental properties as well as similarities and differences between the elements.

Categories within The Periodic Table


Postings: 25

Periodicity refers to the recurring trends seen among the elements of the periodic table.


Postings: 2

Halogens refer to Group 17 in the periodic table consisting of the elements: fluorine (F), chlorine (Cl), Bromine (Br), Iodine (I) and Astatine (At).


Postings: 2

Gas is one of the four fundamental states of matter found between the liquid and plasma states, where their particles are widely separated and have very weak intermolecular bonds between the atoms.

Transition Metals

Postings: 9

Transition Metals refer to any elements found in the d-block of the periodic table.

Atomic Size and Electronic Structure

1. What happens to the atomic radii as you go down a column in the periodic table,e.g. from Li to Fr? 2. Why does the trend you identified in question 1 occur? Be sure to refer to electronic structure in your answer 3. What happens to the atomic radii as you go across a row in the periodic table, e.g. from Li to Ne?

Density and Melting Point

Questions on density: 1. Using the table below determine any trends of density that might be related to the periodic table. Substance Density (g/L) Substance Density (g/L) H2 0.0899 O2 1.429 He 0.1785 N2 1.2506 Ne 0.9

Reactivity of Metals

1. What is the order of activity of the metals in your study? (Arrange them from most reactive to least reactive). Consider the metals used in demonstration - sodium, potassium and calcium in addition to the ones you used in experiment - copper, magnesium, zinc. 2. Why is calcium a poor choice for a metal to be used in pi

Representative Elements

The 'representative elements' are those in the first two columns and the last six of the periodic table. The middle region of the table represents the transition elements. When chemists discuss the periodic nature of the elements they focus on mainly the 'representative elements'. Find two websites that discuss the Perio

Periodic Table

Nearly every compound of silicon has this element in the +4 oxidation state. In contrast, most compounds of lead have this element in the +2 oxidation state. a) What general trend of the oxidation states does this observation illustrate? b) What could you suggest as an explanation for this observation?