Unit 10: Structure, Bonding & Properties Flashcards
What is an atom?
An atom is the basic building block of all substances.
It contains 3 sub atomic particles -
proton - +1 charge, present inside the nucleus
electron - -1 charge, orbits around the nucleus
neutron - 0 charge, inside the nucleus
The mass of an atom is concentrated in the nucleus
What is the atomic number, mass number and neutron number of an atom?
Atomic no. - number of protons/electrons in a neutral atom
Mass no. - number of protons + neutrons in the nucleus of an atom. also known as nucleon number
Neutron no. - number of neutrons in the nucleus of an atom
How is the periodic table arranged?
The periodic table is arranged in increasing order of proton number.
Which subatomic particle is responsible for chemical reactivity?
Electrons are responsible for chemical reactivity.
Define electronic configuration.
The electronic configuration of an atom refers to the arrangement of electrons in an atom.
How can electrons be arranged in an atom?
- The 1st shell (K shell) can accommodate 2 electrons
- The 2nd shell (L shell) can accomodate 8 electrons
- The 3rd shell (M shell) can accommodate maximum 18 electrons (if the element has an atomic number of 21-30)
Define an ion.
An ion is a atom , or a group of atoms, which have a charge.
Define cation and ion. Give an example of each.
Cation - an ion having a positive charge
Anion - an ion having a negative charge
Define valency.
Valency refers to the combining capacity of an atom/element.
What is the octet rule?
The octet rule states that every atom has a tendency to have eight electrons in the outermost shell.
What are the exceptions to the octet rule?
Hydrogen, Lithium, Beryllium, and Boron tend to have 2 electrons in their outermost shell (duplet rule)
Note - If there are 4 electrons in the outer most shell, an atom will not gain or give electrons, instead they will share electrons.
What is chemical bonding? Name its two types.
Chemical bonding refers to the interaction between various atoms to form bonds and create a compound. It’s two types are ionic and covalent. Atoms form bonds to attain stability by filling their balance shells
Define ionic and covalent bonding. give examples of each.
• Ionic bonding refers to the bonding between atoms when they lose or gain electrons. For example - NaCl and CaCl2
• Covalent bonding refers to the bonding between atoms where they share electrons - For example CO2 and H2O
What are the properties of ionic compounds?
- They are brittle in nature
- Lattice is a 3D representation of an ionic compound
- They have very high melting and boiling points
- Most of the ionic compounds are soluble in water
- They conduct electricity in molten or aqueous solutions (when dissolved in water)
What are the properties of covalent compounds?
- They are not brittle in nature
- They have low melting and boiling points
- Most of the covalent compounds are not soluble in water
- They do not conduct electricity
What is a giant ionic structure? (What are lattices)
Most ionic compounds exist as crystals, which are made up of lattices. Lattices are orderly 3D arrangements of ions in space.
Why do ionic compounds have very high melting points?
Since ionic compounds are bound with very strong electrostatic forces of attraction, a lot of energy is needed to break them from these forces. Hence, ionic compounds have very high melting points.
Why are ionic compounds brittle?
On applying a force to the ionic structure, the lattice arrangement of the atom is broken and similar charges come together, causing a repulsion which breaks the structure easily. Hence, ionic compounds are brittle.
What are simple covalent structures? Give examples.
Simple covalent structures are small covalent molecules which exist in simple structures with weak forces of attraction between the molecules.
Examples - CO2 (carbon dioxide), O2 (oxygen), N2 (Nitrogen), NH3 (Ammonia), CH4 (Methane)
What are giant covalent structures? Give examples.
Giant covalent structures are covalent molecules which exist as huge networks of atoms bonded together.
Examples - diamond, graphite, Sand (SiO2 - quartz as well)
Why do giant covalent structures have high melting points?
Due to giant covalent structures being very big networks, and having a large size, it requires a huge amount of energy to break the bonds, causing it to have a high melting point.
What are the properties of the giant covalent compound:
Diamond
- Made up of only Carbon atoms that are bonded in a tetrahedral manner
- It is the hardest naturally occurring substance
- It is an insulator (does not conduct electricity) because each carbon is bonded with 4 other carbon atoms, hence there are no free electrons
- High melting point
What are the properties of the giant covalent compound:
Graphite
- Made up of only carbon atoms that are bonded together in a layered hexagon manner.
- It is slippery in nature because of the weak forces of attraction between the layers.
- It is a good conductor of electricity because in the structure of graphite, each carbon is bonded to 3 other carbon atoms and one electron is free to move, which helps in the conduction of electricity.
What is metallic bonding? How are metallic structures arranges?
Metallic bonding refers to the bonding between metal atoms.
In metallic structures, atoms are arranged side-by-side in a regular repeating pattern. The electrons are free to move around. They are termed as a ‘sea of electrons.’
