How the patterns in atomic structure may have helped to design periodic table and predict the trends in properties of elements?
number of shells
electronic configuration
reactivity and metals
as we move down, the number of shells increase. the number of shells can tell us where the elements is supposed to be positioned.
every group starts from one shell and then increase by one. this can help us to position the elements.
as we move from left to right in the periodic table, the number of shells remain the same but the electrons on the outermost shell increase.
for example, we have two elements. sodium and argon. both these elements are from the same period. Sodium is in the start of the period and argon is that last. this period has eight elements in it and the first element which is sodium has one electron in the outermost shell and as we move to the last, the number in the outermost shell increase and argon has eight electrons in the outermost shell.
for example, a element has 2 shells and another element has 4 shells. from this, we can see that the element with 2 shells with be above the element with 4 shells and there would be a space in-between for the element with 3 shells for the particular group.
in for example sodium, the number of shells is 3. the electrons in the outermost shell is 1. the first shell can only have two 2 electrons and the other shells can only have 8 electrons so to write the electronic configuration of sodium we write 2,8,1. it goes in order starting from one shell.
metals have a high reactivity so if an element is a metal it will have a high reactivity and will be positioned in group 1. group 1 elements are metals and have a high reactivity.
if the element is a non-metal but has a high reactivity then it would be positioned in group 7. group 7 elements are nonmetals and have a high reactivity
Force of attraction
metallic character
number of electron, protons and neutrons
Density
Melting and boiling point
The number of protons, neutrons and electrons can tell us a lot about the position of the elements in the periodic table.
electrons
the number of electrons can tell us the position of the element across the period. as talked in the electronic configuration, the number of electrons predict the placement of the element with the number of electrons in the outermost shell.
protons and neutrons
protons and neutrons can tell us the mass number help us position the element.
protons
protons help us know the atomic number which is very helpful and we move from left to right and then move to the next period and then again move from left to right, the atomic number increases by 1. for example, hydrogen(the first element in the periodic table) has the atomic number as 1. then, helium(the second element in the periodic table) has a atom ic number as 2. this continues till the end and will really help us in placing the elements.
group 1
group 7
melting point and boiling point both generally increase as we move down group 6 and 7.
melting point and boiling point both decrease gradually as we move down group 1 and 2.
transition metals
melting point and boiling point both generally increase as we move up group 3, 4 and 5.
as we move down the periodic table, the metallic character increase because the nuclear charge experienced by valence electrons decreases as the outermost electrons in the outermost shells move further away from the nucleus. this happens because the number of shells increase as we move down a group. Therefore, these electrons can be lost easily.
as we move across the periodic table, the metallic character decreases because the nuclear charge experienced by the valence shell electrons increase as the electrons in the outermost shell remain the same distance. this is because the number of shells remain the same as we move across the period. therefore, the tendency to lose electrons decreases.
As we go down a group the distance between the nucleus and valence electrons increases. this is because the number of shells increase. though the charge remains same. this weakens the force of attraction and the valence electron is held with less force because the valence electron gets further away.
the density increases as we go down group. this is because both mass and volume are increasing as we move down a group, and density is mass upon volume so if the mass and volume increase, then the density increases too. the mass number increases as we move down the group because mass is the number of protons and neutrons so if they increase the mass increases.
as we move across a period, the distance between the nucleus and the valence electrons remains the same but the charge increases. As a result the force of attraction between the nucleus and the valence electrons increases across a period.
as we move across a period, electrons are added one at a time to the outermost shell. Since the number of protons is also increasing, the nuclear charge increases across a period. This causes the atomic radius to decrease. If radius decreases across a period and the atomic number increases, then density increases as we move across the period.