Flashcards in Topic 1.1- Bonding Deck (26)
what are ions?
ions are atoms or molecules with an electric charge due to the gain or loss of electrons. If electrons are lost, the ion has a positive charge. Metals tend to do this, so they form cations (positive ions). If electrons are gained, the ion has a negative charge. Non-metals tend to do this, and they form anions (negative ions)
what do elements from groups 1-3 form?
what do elements from 5-7 form?
what is oxidation?
the process of an atom losing an electron/s and becoming a positively charged ion
what is reduction?
the process of an atom gaining an electron/s and becoming a negatively charged ion
how can you deduce the charge of an atom from the electronic configuration of the atom from which the ion is formed?
so if the electronic configuration is 2.8.1, you can see that the atom has one outer shell electron only. And so it only needs to lose that one to have a full outer shell, making an ion with the electron configuration 2.8 with a positive 1 charge
when does ionic bonding occur?
ionic bonding happens with oppositely charged ions because they are attracted to each other because of their opposite charges (electrostatic attraction) which bonds them to form an ionic compound
why do ionic compounds have high melting and boiling points?
the electrostatic attraction keeps the ions bonded, and as it is very strong, it takes a lot of energy to break these bonds. For this reason, ionic compounds have very high melting and boiling points, because of the amount of energy needed to break these strong bonds between oppositely charged ions
what is a covalent bond?
a shared pair of electrons between two non-metal atoms. If each atom shares two electrons, it is called a double covalent bond. eg. in oxygen, as each oxygen atom has 6 outer shell electrons it shares 2 electrons to have 8 as a full outer shell. Hence oxygen is diatomic: 02
why are covalent bonds so strong?
each of the positively charged nuclei is attracted to the same negatively charged pair of electrons, which is why covalent bonds are so strong. The atoms come close enough for their outer electron (valence) shells to overlap
why does hydrogen form molecules?
whenever a bond is formed energy is released, and that makes the things involved more stable than they were before. The more bonds an atom can form, the more energy is released and the more stable the system becomes. In the case of hydrogen, each hydrogen atom has only one electron to share, so it can only form one covalent bond. The H2 molecule is still much more stable than two hydrogen atoms
what is the significance of noble gas structures in covalent bonding?
the formation of covalent bonds producing noble gas structures is quite common. When atoms bond covalently, they often produce outer electronic structures the same as noble gases full outer shell. This is so they become stable and unreactive. The more electrons shared, the more covalent bonds there are, the more stable the molecule is
what happens during covalent bonding?
during covalent bonding, the sharing of 2 electrons between 2 non-metals, the electrons become attached to the nucleus of each ion in a bond, this is electrostatic attraction.
what properties do simple molecular structures usually have?
low melting and boiling points
why do simple molecular structures have low melting and boiling points?
the forces of attraction between molecules (intermolecular forces) are weak and therefore very little energy is required to overcome them. Although, when simple molecular substances change state, the covalent bonds between the atoms are not usually broken. Covalent bonds are strong compared to the forces of attraction between the molecules
what states have simple molecular structures?
gases, liquids and solids with low melting points
why do giant covalent structures have high melting and boiling points?
because when melting or boiling it, you are not separating inter-molecular bonds between the atoms, but the inter-molecular bonds that keep the molecule together. There are a lot of these, therefore they have high melting and boiling points
what are giant molecular structures?
substances made up of millions of atoms covalently bonded together to form a giant strucutre
how are metals structured?
metals have a giant, three-dimensional lattice structure in which positive ions are arranged in a regular pattern in a 'sea of delocalised electrons'. The outer shell electrons are detached from the atoms and are delocalised throughout the structure. The attraction between the positive ions and the delocalised electrons is known as a metallic bond and this attraction keeps the ions together
why are metals good conductors of electricity?
because the delocalised electrons are free to move when a potential difference is applied across the metal
why are metals malleable?
they are malleable and ductile because the layers of positive ions can easily slide over one another and take up different positions. The delocalised electrons move with them so the metallic bonds are not broken
what does malleable mean?
able to be hammered or pressed permanently out of shape without breaking or cracking
what does ductile mean?
able to be drawn out into a wire
how can metals be made harder?
by alloying them with other metals. An alloy is a mixture of metals. In an alloy, the different metals have slightly different sized atoms. This breaks up the the regular arrangement and makes it more difficult for the layers to slide.
what are the properties of non-metals?
- react with oxygen to form acidic oxide
- dull sound when hit with hammer
- low melting and boiling points
- poor conductors of electricity
- poor conductors of heat
- solids, liquids and gases at room temp
- dull looking
- when they form ions, the ions are negative (apart from hydrogen)
- low density