Trends Down a Group

As you go down a group the atomic size of the atom +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker. This is because a new or extra shell of electrons is +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker for each step down the group. The extra shell is located +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker and away from the nucleus. Although the Nuclear Charge increases as you go down a group the +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker or also called the Core Charge remain the same for the elements in the same group. For instance in the case of group I elements, namely; lithium, sodium and potassium atoms, the Nuclear Charge increases as you go down the group but the Core Charge attracting the valence electrons (also called the electrons in the outermost shell and these are the ones involved in chemical reactions) remain the same with the value of +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker. This is because shells inner than the outermost shell +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker the outermost electrons from the full attractive force of the nucleus. The atomic radii becomes +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker.

As you go down a group the Ionization Energy +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker. As the atom gets larger the outer electrons are further away from the nucleus and +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker energy is required to remove the most loosely bound electron from the atom.

As you go down a group the metallic nature will +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakercrease. This is because the Ionization Energy +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakercreases as you go down a group. This change is obvious when we study the properties of Elements in Group 14. In Group 14 we start with the +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker called carbon at the top and reach the metal lead at the bottom.

Electronegativity is another attribute of elements. Electronegativity is the electron +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker ability of atoms and this +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakerreases as you go down the group. Not to forget the atomic size +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakerreases as you go down the group and the Effective Nuclear Charge which remain the +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker as you go down the group is increasingly spread out over a greater surface area. Hence, the electron attracting ability of that atom gets +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker.

Trends Across a Period From Left to Right

As you go across a period the atomic size +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakereases. This is because the number of protons increase as you across the period. Although the number of electrons +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakerease as you go across the period these electrons are added to the +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakere shell. Hence the electrons are attracted closer to the nucleus. This means that an atom of argon is +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker than an atom of sodium despite the greater mass of argon.

As you go across a period the ionization energy +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakerases. As you go across the period the hold of the protons on the electrons gets +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker. This is because the Nuclear Charge and the Core Charge increases. As the atomic radius get smaller the electrons located in the valence shell of any other atom coming towards it can get +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker to the nucleus of the attracting atom. The attracting atom can easily attract the +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker electron.

The Electronegativity or electron attracting ability of an atom will then incr+1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker across a period from left to right.

The metallic nature will +1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweakerase as you go across the period. This is because electrons are held more strongly to the atom as you go across a period. Due to the high ionization energy the elements get l+1addedattractingcloserdedecdecrdecredecreaseseaseEffective Nuclear Chargeessfurther outinincincomingincrincreincreaseslargerlessnon metalsamsameshieldsmallerstronger and strongerweaker metallic. Hence, magnesium is less metallic than sodium and chlorine is a non metal.


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