The periodic table Flashcards
Key concepts in chemistry
Abundance
Definition
If there is a lot of something, it is described as being abundant.
Atom
definition
The smallest part of an element that can exist.
Atomic number
definition
The number of protons and neutrons in the nucleus of an atom. Also called the atomic proton number.
Chemical properties definition
A description of how a substance reacts with other substances. For example, flammability, pH, reaction with an acid, etc.
Compound
Definition
A substance formed by the chemical union of 2 or more elements.
Electron
definition
Subatomic particle with a negative charge and a negligible mass relative to protons and neutrons.
Electron arrangement configuration
Definition
The order electrons are arranged into between different energy levels(shells).
Element
definition
A substance made up of one type of atoms only.
Group
(periodic table)
Definition
A vertical column in the periodic table containing elements with similar chemical properties.
Isotope
Definition
Atoms of an element with the same number of protons and electrons but different numbers of neutrons.
Metal
Definition
Shiny element that is a good conductor of electricity and heat, and which forms basic oxides.
properties
Definition
The characteristics of something. In chemistry, chemical properties include the reactions a substance can take part in. Physical properties include colour and boiling point.
physical properties
Definition
A description of the appearance of a substance or how it acts without involving chemical reactions. For example, state, melting point, conductivity, etc.
periodic trend
definition
A pattern in chemical or physical properties of elements in the periodic table.
period
definition
A horizontal row in the periodic table.
nucleus
Definition
The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.
non-metal
Definition
Element that is a poor conductor of electricity and heat, and which forms acidic oxides.
proton
Definition
Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1.
relative atomic mass
Definition
The mean relative mass of the atoms of the different isotopes in an element. It is the number of times heavier an atom is than one-twelfth of a carbon-12 atom.
Who is Dmitri Mendeleev?
Like many scientists working at the end of the 19th-century the Russian chemist Dmitri Mendeleev (1834-1907) was looking for ways to organise the known elements. Mendeleev published his first periodic table of the elements in 1869.
Features of Mendeleev’s tables
Mendeleev arranged the elements in order of increasing relative atomic mass. When he did this he noted that the chemical properties of the elements and their compounds showed a periodic trend. He then arranged the elements by putting those with similar properties below each other into groups
Features of Mendeleev’s tables
To make his classification work Mendeleev made a few changes to his order:
- he left gaps for yet to be discovered elements
- he switched the order of a few elements to keep the groups consistent
Features of Mendeleev’s tables
Predictions using gaps
Mendeleev left gaps in his table to place elements not known at the time. By looking at the chemical properties and physical properties of the elements next to a gap, he could also predict the properties of these undiscovered elements. For example, Mendeleev predicted the existence of ‘eka-silicon’, which would fit into a gap next to silicon. The element germanium was discovered later. Its properties were found to be similar to the predicted ones and confirmed Mendeleev’s periodic table.
Features of Mendeleev’s tables
Pair reversals
Iodine has a lower relative atomic mass than tellurium. So iodine should be placed before tellurium in Mendeleev’s tables. However, iodine has similar chemical properties to chlorine and bromine. To make iodine line up with chlorine and bromine in his table, Mendeleev swapped the positions of iodine and tellurium.
How are elements arranged in a modern periodic table?
In the modern periodic table, the elements are arranged according to their atomic number
In the periodic table the elements are arranged into:
rows, called periods, in order of increasing atomic number
vertical columns, called groups, where the elements have similar properties
In the periodic table, what are periods?
Rows, in order of increasing atomic number
In the period table, what are groups?
Vertical columns, the elements have similar properties
Metals and non-metals in the periodic table
The metal elements are found on the left hand side of the periodic table, and the non-metal elements are found on the right. Imagine a zig-zag line, starting at B-Al-Si, separating metals from non-metals.
Mendeleev
Isotopes
Mendeleev did not know about isotopes, but their existence is an explanation for pair reversals in his table.
The positions of iodine and tellurium were reversed in Mendeleev’s table because:
- iodine has one naturally occurring isotope, iodine-127
- the most abundant tellurium isotopes are tellurium-128 and tellurium-130
What is the way in which electrons are arranged in an atom called?
Electron configuration
Predicting an electronic configuration
The electronic configuration of an atom can be predicted from its atomic number.
How is the electronic configuration feature: Number or numbers of circles linked to the periodic table?
Link to the periodic table:
Period number
How is the electronic configuration feature: Number of electrons in outermost shell linked to the periodic table?
Link to the periodic table:
Group number
How is the electronic configuration feature: Total number of electrons in all shells linked to the periodic table?
Link to the periodic table:
Atomic number
The electronic configuration of sodium is (2.8.1)
List it’s period, group and atomic number
sodium, Na:
- is in period 3
- is in group 1
- has an atomic number of (2 + 8 + 1) = 11
Which electrons meet and interact when atoms collide and react?
When atoms collide and react, it is the outer electrons that meet and interact.
Elements in the same group have similar, what?
why?
Elements in the same group have similar chemical properties because they have the same number of electrons in their outer shell.
What order did Mendeleev place the elements in to form his first periodic table?
Mendeleev placed the elements in order of increasing atomic mass.
How are the elements arranged in the modern periodic table?
In the modern periodic table the elements are arranged in order of increasing atomic number.
Why did Mendeleev leave gaps in his periodic table?
Mendeleev realised that there were still some elements to be discovered. When the elements were discovered their properties matched the predicted properties.
What is the electron arrangement of an element with an atomic number of 16?
2.8.6
What name is given to the horizontal rows in the periodic table?
Periods
Where is the element with the electron arrangement: 2.8.8.2 found in the periodic table?
The element is found in period 4 and group 2
Which part of the atomic structure has most effect on the chemical properties and reactions of an element?
The outer electron shell
What changes in atomic structure occur as you move from left to right along the horizontal rows in the periodic table?
The number of protons in the nucleus increases by one.
What changes in atomic structure occur as you move from top to bottom along vertical rows?
The number of electron shells increases by one each time you go down into the next period.
