Flashcards in Particles and Atoms Deck (45):
What sort of gases did the atmosphere contain around the time of the Big Bang?
carbon dioxide, water, nitrogen, methane, ammonia, hydrogen cyanide
Briefly explain how DNA was first formed (and what DNA stands for.
DNA (Deoxyribo Nucleic Acid), a very complex molecule, was formed when small molecules joined together over time.
Where is DNA found?
In all cell nuclei
What is the photosynthesis equation?
6H2O + 6CO2 - C6H12O6 + 6O2
Talk a little about carbon dioxide.
Carbon dioxide undergoes sublimation (straight from solid to gas and vice versa). Solid CO2 is called dry ice. It is used in fire extinguishers.
Talk a little about nitrogen.
It is an unreactive gas which can be converted into ammonia which is used to make fertilisers.
Talk a little about oxygen.
A gas that will combust (burn) a fuel.
Talk a little about phosphorus.
It burns with a bright flame in oxygen, making phosphorus oxide which is used to make fertilisers.
Talk a little about sulphur.
It burns with a blue flame in oxygen, forming sulphuric dioxide which is used to make sulphuric acid (H2SO4) which is used in car batteries and is also one of the gases that causes acid rain.
What is an element?
An element is a substance made up of only one kind of atom.
So far, how many element do chemists know of?
about 105 elements (about 90 of which are found in the Earth and atmosphere naturally and about 30 of which have been artificially made in a lab)
What categories do the left, middle and right of the periodic table represent?
On the left side, there are the metals. In the middle, we find the semi-metals. And on the right, there are the non-metals.
What simple test can one carry out to determine which group (metal or non-metal) and element belongs to?
You have an electric circuit with a bulb and two clips. If the element attached to the two clips is a metal, the bulb lights up. If the element is a non-metal, it doesn't light up. (Metals conducts electricity)
What is the most common element in the Earth's crust and in the human body?
What is the most common metal in the Earth's crust?
What is the most common metal in the human body?
What are atoms?
Atoms are the smallest particles of matter, that we cannot break down further by chemical means.
What is the difference between a mixture and a compound?
A mixtures is made from different substances that are not chemically joined whereas a compound is made of atoms of different elements, bonded together.
What does the name of a compound with 2 elements end in?
What does the name of a compound with oxygen end in?
How many atoms are needed, joined end to end, to measure 1cm?
one hundred million atoms
Which element has the smallest atoms? What is the mass of each atom of this element?
Hydrogen atoms have a mass of about 1.7 * 10^-24 g
What charge does a proton have and what is its approximate mass in amu?
A proton has a charge of +1 and a mass (amu) of about 1
What charge does an electron have and what is its approximate mass in amu?
An electron has a charge of -1 and a mass (amu) of about 1/1800th of a proton/neutron
What charge does a neutron have and what is its approximate mass in amu?
A neutron has no charge and has a mass (amu) of about 1
How does an atom hold its form?
The forces of attraction that hold the particles in an atom together are electrostatic. Positive protons in the nucleus attract the negative electrons around it.
How are there so many different elements?
By changing the number of protons, neutrons and electrons in the atoms.
What is the atomic number?
It is the number of protons found in the nucleus of an atom. The atomic number also represents the number of electrons found in the rings of an atom since the number of protons and electrons in an atom is are always the same.
What is the mass/nucleon number?
It is the total number of protons and neutrons in the nucleus of an atom. This is the atomic mass (total mass) of an atom since electrons have practically no mass.
What are isotopes? Give an example.
Isotopes are atoms of the same element which have the same amount of protons, but a different amount of neutrons/nucleon number. For example, all carbon atoms have 6 protons, but some have more neutrons than others. These different atoms are called isotopes of carbon.
How does the reactivity of different isotopes of an element vary?
It doesn't - the reactivity of different isotopes of an element is identical because they have the same number of electrons.
What is the relative atomic mass?
The relative atomic mass of an element is the average mass of its naturally occurring isotopes, relative to the mass of a carbon-12 atom.
How are electrons arranged in an atom?
The closer the electrons are to the nucleus, the less energy they have. The first energy level/electron shell nearest the nucleus can contain a maximum of 2 electrons. The second one can hold a maximum of 8. The third and others can contain even more (but for the purposes of IGCSE, we'll restrict that number to 8)
Which electrons are used in a reaction? Why?
Only the outer electrons. The inner electrons are very stable (their shells are full, unlike the outer shell, with the exception of group 8/0 atoms) and are not involved in chemical reactions.
What is the last group of the periodic table called? Why is it called this?
It is sometimes called group 0 (other times group 8) because its outer electron shell is either full or empty.
What relation does an element's group number and its number of electrons in its outer shell have?
These numbers are the same. For example, group 1 (alkali metals) in the periodic table is called group 1 because the elements in this group all have one electron in their highest energy level.
Why does hydrogen appear in both group I and group VII?
Because, firstly, like alkali metals (group I), it needs to lose one electron to be stable, or, like halogens (group VII), it needs to gain one electron to be stable. This similarity makes hydrogen and halogens behave similarly in a reaction.
How does the atomic number evolve throughout the periodic table?
It increases by 1 across the periodic table (from left to right)
How does the relative atomic mass evolve throughout the periodic table?
It increase across the periodic table by various numbers.
What happens when elements are arranged according to their electron configuration in the periodic table?
Elements with similar chemical properties occur in the same groups of the periodic table.
What do neutrons do in the atom.
As they are uncharged, neutrons do not affect the electrical balance of an atom. They just add to the atomic mass and act as a glue to hold the atoms together.
What is the molar mass?
Used in an equation to find moles, the molar mass is essentially the relative atomic mass in g/mol.
What is a mole?
A mole of a substance is the amount that contains the same number of units as the number of carbon atoms in 12g of carbon-12.
How do you calculate the number of moles of a substance?
Divide the mass (g) by the relative atomic mass.