chemistry lessons 1-5

Bohr’s model of the atom- mass and positive charge

mass and positive charge of the atom concentrated in a central area called the nucleus

Bohr’s model of the atom- electron orbit

negatively charged electrons orbit the nucleus in different energy levels or at specific distances from the nucleus

Bohr’s model of the atom- electron closest

the electrons closest to the nucleus have the lowest energy levels

proton

found in the nucleus, mass of 1 and electric charge of +1

neutron

found in the nucleus, mass of 1, and electric charge of neutral

electron

found in the electron cloud, mass of 1/2000, and electric charge of -1

where is all of the mass of the atom located?

in the nucleus

atomic number

number of protons in the nucleus

mass number

number of protons and neutrons in the nucleus (mass of the atom)

number of protons is

equal to the atomic number

number of neutrons

mass number - atomic number

number of electrons

equal to the number of protons and therefore the atomic number (in a neutral atom)

electron configuration

used to describe the arrangement of electrons within the atom

each energy level/ or energy shell can hold a

maximum number of electrons

shell 1 (closest to the nucleus) holds

2 electrons

shell 2 holds

8 electrons

shell 3 holds

8 electrons

shell 4 holds

18 electrons

valence electrons

the electrons in the outer shell of an electron

an atom that has a full outer shell is very stable and this electron arrangement is called

noble gas configuration

groups

vertical columns in the periodic table

horizontal rows in the periodic table are called

periods

what do elements in one group of the periodic table have in common?

they have the same number of valence electrons

what do elements in one period of the periodic table have in common?

they have the same number of energy levels (shells)

what is the difference between an atom and an ion?

atoms are neutral whilst ions have charge

why do ions form?

so that the atoms can become stable and gain a full outer shell

why do metals for positive ions and what are they called?

metals lose electrons which means they form positive ions. these are called cations.

why do non-metals form negative ions and what are these ions called?

non-metals gain electrons, meaning they form negative ions. these ions are called anions

what is meant by the term noble gas configuration?

there is a full outer shell

The Alkali Metals (Lithium, Sodium, Potassium)

These elements form ions with a charge of +1 by losing a single electron. They have typical metallic properties and display similar extreme chemical behavior. Because of their high reactivity, they are not found in their pure forms in nature but only as compounds.

The Alkaline Earth metals- berrylium, magnesium and calcium

are similar to the alkali metals in that they produce alkaline solutions. However, they are less reactive than Group 1 metals. As you move down the group, their reactivity increases, but they generally have higher melting and boiling points compared to the alkali metals.

group 14, carbon, silicon, germanium

The properties of these elements vary down the group. Carbon is a non-metal, silicon and germanium are metalloids, while tin and lead are metals. This group shows a gradual change from non-metallic to metallic character as you go down the group.

the halogens, fluorine and chlorine

These elements form ions with a charge of −1 and are not found in their pure form in nature, but are commonly found in salts like sodium chloride (NaCl). As you go down the group, halogen atoms get larger and less reactive. They form diatomic molecules (e.g. F₂, Cl₂, Br₂, I₂) and often have coloured, poisonous vapours.

novle gases

are extremely stable and only react under very rare, extreme conditions. Helium has a very low density, which is why it’s used in balloons. As you move down the group, the density of the noble gases increases.