What is Lewis Dot Structure


Lewis Dot Structure 101

Lewis Structure or Lewis Dot Structure is a formula developed to concretely express the bond formation between chemical species (atom, molecule, ion).

This formula is to show the electrons in the last layer of the atom with dots around the symbol of the atom. In this way; The number of electrons in the last layer of the atom, the desire to enter into chemical reactions with other atoms, how many electrons it will gain/give or use in common if it interacts with other atoms can be easily understood.

According to the Lewis Dot Structure;

A dot is placed around the atom symbol for each valence electron. E.g; Lewis dot structure of a Lithium (3Li) atom with 1 electron in its outer shell;

The electrons of atoms with 2 electrons in the last layer should be placed as far away from each other as possible. E.g; Lewis dot structure for boron atom with 3 electrons in its last layer;

Electrons are placed in the 4 corners of the symbol in order, starting from anywhere. In cases where the number of electrons is more than 4, the dots are written in pairs in order.

Lewis Dot Structure of Ions and Ionic Bond

Ions are atoms and groups of atoms that carry positive (+) or negative (-) charges. An ionic bond is formed when atoms (metal and nonmetal) come together and form a bond. Like the Lewis Dot Structures of atoms, the Lewis Dot Structures of ions are represented by as many dots as the number of electrons they have. In this notation, the iodine charge must be written. E.g; Formation of Ca2+ and Cl- ions and Lewis dot structure of calcium chloride (CaCl2) compound formed by these ions;

When each calcium atom transfers its valence electrons to two chlorine atoms, positively charged calcium ions and negatively charged chlorine ions are formed, and the oppositely charged ions exert an electrostatic attraction on each other, forming a calcium chloride crystal.

Likewise, in the reaction of magnesium (Mg) and oxygen (O), each magnesium atom loses two electrons to obtain a fully filled outer layer. In the meantime, each oxygen atom gains 2 electrons and the oppositely charged Mg2+ and O2- ions now attract each other. The net charge of the magnesium oxide compound formed becomes zero.

When sodium and chlorine atoms come together to form sodium chloride (Na+Cl-/table salt), one valence electron of each sodium atom is transferred to the valence electron layer of a chlorine atom. Practically, the representation of the electrons in these layers is as follows;

Since the ions formed are armor-charged, they attract each other with an electrostatic attraction force, forming a sodium chloride crystal. The resulting crystal consists of an incalculable number of sodium and chlorine ions.

Formation of Covalent Bond and Lewis Dot Structure

Since nonmetal atoms are prone to gain electrons, they share electrons among themselves. The bond formed between the same or different types of nonmetals as a result of sharing their electrons is a covalent bond. The covalent bond between atoms is a strong interaction, since the prorons of both atoms exert an electrostatic force of attraction on the shared electrons.

Nonmetal atoms reach the maximum number of electrons in their last layer by sharing their valence electrons. The shared electrons now belong to both atoms. Molecules are formed by covalent bonding. The Lewis dot structures of atoms can be used to determine how many of the valence electrons will form covalent bonds. For example; The fluorine atom (9F), which has 7 electrons in its last layer, fills the layer capacity if it can have one more electron. For this, 1 electron belonging to the other nonmetal atom can be used in common.

We mentioned that nonmetal atoms are used together in covalent bond. The electron suitable for common use in the Lewis dot structure is the lone one. Lewis dot structure of fluorine atoms and covalent bonds;

The shared electrons in a covalent bond are called electron pairs (bonding pairs or shared pairs). In the Lewis structure, every two points between two atoms, that is, every two electrons shared, represents a chemical bond. This bond can also be represented by a line. E.g; Ammonia molecule consisting of nitrogen and hydrogen atoms; In the NH3 molecule, three nitrogen atoms form and each hydrogen atom forms one covalent bond.

As a result, the formula of the compound formed by nitrogen with hydrogen is NH3. Each nitrogen atom fills its electron capacity by sharing its single electrons with three hydrogen atoms.