Topic 1 - Key concepts of Chemistry Flashcards
What was Dalton’s model of the atom like?
- atoms cannot be broken down into anything simpler - the atoms of a given element are identical to each other - the atoms of different elements are different from one another during chemical reactions atoms rearrange to make different substances.
Why has Daltons’s model of the atom changed?
The Dalton model has changed over time because of the discovery of subatomic particles.
Where are the subatomic particles located?
Neutron - Nucleus Proton - Nucleus Electron - Shells orbiting the nucleus
What is the mass and charge of a proton?
Mass - 1 Charge - 1
What is the mass and charge of a neutron?
Mass - 1 Charge - 0
What is the mass and charge of a Electron?
Mass - 0.0005 Charge - (-1)
Which two subatomic particles are of equal number in a neutral atom?and why?
Protons and Electrons. This is so that the atom is in a neutral state as it has a charge of 0.
Where is most of the mass of an atom concentrated?
The mass of electrons is very small compared to protons and neutrons. Since a nucleus contains protons and neutrons, most of the mass of an atom is concentrated in its nucleus.
What is the mass number?
The mass number is the number above the element symbol on the periodic table. It tells you the total number of neutrons and protons in an atom.
What is the atomic number?
The stomic number is the number below the element symbol on the periodic table. It tells you the total number of protons in an atom.
What must every atom of the same element have in common?
The same number of protons, the number of protons is unique to each element.
What is the relative atomic mass?
The relative atomic mass of an element is the weighted average of the relative atomic masses of the isotopes in the element. This means that some relative atomic masses are not whole number
What are isotopes?
Isotopes are different forms of the same element, which have the same number of protons but a different number of neutrons. They have the same atomic number but different mass numbers.
What are the main differences between Mendeleev’s periodic table and the modern periodic table?(4)
- The current periodic table has its elements ordered in increasing atomic number whereas Mendeleev’s periodic table has its elements ordered in increasing atomic weight. - More elements have been discovered and added in the current periodic table: such as the noble gases group 0. - There are no gaps in the current periodic table. The gaps in Mendeleev’s table have been filled by the elements that were discovered. - Transition metals have been listed in a separate block whereas Mendeleev included them with other elements.
How did Mendeleev use his table to leave gaps for undiscovered elements?
Mendeleev left gaps in his table to place elements not known at the time. By looking at the chemical properties and physical properties of the elements next to a gap, he could also predict the properties of these undiscovered elements.
Why did Mendeleev reverse some pairs in his table instead of following the trend of increasing atomic weight?
When he ordered elements to increasing atomic weight, he noted that the chemical properties of the elements and their compounds showed a periodic trend. He then arranged the elements by putting those with similar properties below each other into groups so he had to switch the order of a few elements to keep the groups consistent.
What are groups and periods?
The rows of elements in the periodic table, called periods, are in order of increasing atomic number. The vertical columns of element in the periodic table, called groups, are where the elements have similar properties.
Where are metals and non-metals?
The metal elements are found on the left hand side of the periodic table, and the non-metal elements are found on the right. Imagine a zig-zag line, starting at B-Al-Si, separating metals from non-metals.
What is the limit for the number of electrons in the first three shells?
1st- 2 electrons 2nd- 8 electrons 3rd - 8 electrons
How can you work out the electronic configuration of an element using its period and group?
The number of shells which contain electrons is the same number as the period of the element. The group number tells you how many electrons ocupy the outer shell of an element.
What is a covalent bond?
A covalent bond is a bond that forms when a pair of electrons is shared between non-metal atoms.
What are simple covalent structures?
These are made of molecules containing a few atoms joined together by covalent bonds.
Give six examples of Simple Covalent Structures.
- Hydrogen - Water - Hydrogen Chloride - Oxygen - Methane - Carbon dioxide
Draw the structure of hydrogen (scs) in dot cross diagrams
Hydrogen - H2. Hydrogen atoms have one electron, so they need one more to complete the first shell. They can form a single covalent bond with another hydrogen atom to achieve this.
Draw the structure of water (scs) in dot cross diagrams
Water - H20. In water molecules, an oxygen atom shares a pair of electrons with two H atoms to form each two single covalent bonds
Draw the structure of methane (scs) in dot cross diagrams
Methane - CH4. Carbon has four outer electrons, which is half a full shell. It can form four covalent bonds with hydrogen atoms to fill up its outer shell.
Draw the structure of hydrogen chloride (scs) in dot cross diagrams
Hydrogen Chloride - HCl. This is very similar to H2 - both atoms only need one more electron to complete their outer shells.
Draw the structure of oxygen (scs) in dot cross diagrams
Oxygen - O2. An oxygen atom needs two more electrons to complete its outer shell. In oxygen gas, each oxygen atom forms a double covalent bond (a bond made of two shared electron pairs) with another oxygen atom.
Draw the structure of carbon dioxide (scs) in dot cross diagrams
In carbon dioxide molecules, a carbon atom shares two pairs of electrons with two oxygen atoms to form two double covalent bonds
