Test 1 Flashcards
Define isotopes
each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.
Explain atomic structure
Nucleus contains protons and neutrons
Electrons move around the nucleus in an electron shell
( protons and electrons are equal amount)
Give examples of isotopes
- Carbon 12 and Carbon 14 are both isotopes of carbon, one with 6 neutrons and one with 8 neutrons
- Hydrogen 1, 2 and 3
- Oxygen 16, 17 and 18
- Neon 20, 21 and 22
Define protons
A stable subatomic particle occurring in all atomic nucleus, with a positive electric charge equal in magnitude to that of an electron.
Define neutron
A subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.
Define electrons
A stable subatomic particle with a negative charge, found in all atoms in the electron shell.
Define electron configuration
Electron configuration refers to the amount of electrons held per electron shell.
What is the electron configuration for elements up to 20
2,8,8,2
What is the electron configuration for elements 21 to 38
2,8,18,8,2
What is the electron configuration for elements 39 to 56
2,8,18,18,8,2
Define valence electrons
The electrons in the outermost shell of an atom
What is the lewis structure
When the elements symbol is placed in the middle and one dot is drawn to represent each valence electron
What are ions
An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
Explain ion formation
Ions are electrically charged particles formed when atoms lose or gain electrons. They have the same electronic structures as noble gases. Metal atoms form positive ions, while non-metal atoms form negative ions. The strong electrostatic forces of attraction between oppositely charged ions are called ionic bonds.
Define relative atomic mass
The ratio of the average mass of one atom of an element to one twelfth of the mass of an atom of carbon-12.
How do you calculate relative atomic mass
Ar(x)= %A x Ar(a) + %B x Ar(b) / 100
Define mass spectrometry
Mass spectrometry (MS) is an analytical chemistry technique that helps identify the amount and type of chemicals present in a sample by measuring the mass-to-charge ratio and abundance of gas-phase ions.
What 4 stages occur in the mass spectrometer
Ionisation
Acceleration
Deflection
Detection
Basic outline of what happens in the mass spectrometer
Atoms and molecules can be deflected by magnetic fields - provided the atom or molecule is first turned into an ion. Electrically charged particles are affected by a magnetic field although electrically neutral ones aren’t. It goes through 4 stages
Mass spectrometer: ionisation
The atom or molecule is ionised by knocking one or more electrons off to give a positive ion. This is true even for things which you would normally expect to form negative ions or never form ions at all. Most mass spectrometers work with positive ions.
Mass spectrometer: acceleration
The ions are accelerated so that they all have the same kinetic energy.
Mass spectrometer: deflection
The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected.
Mass spectrometer: detection
The beam of ions passing through the machine is detected electrically.
Define spectral analysis
The analysis of a spectrum to determine the properties of its source, such as the analysis of the emission spectrum of a substance to determine the electron distribution in its molecules
Explain spectral analysis
The energy of each level is different for different elements. As a result, the energy absorbed and released in the electron transitions of a given element are unique for this reason an elements light spectrum is like an atomic fingerprint.
When elements are burnt the electrons become excited, when the electrons return to their ground state and emit light of a specific wave length therefore producing specific colours.
What is the flame test
Vaporised salts are sprayed into a hot, almost colourless flame causing the electrons to become excited. When they return to their ground state they emit a specific wave length and producing a unique colour. This makes identifying the element much easier.
What are some trends of the periodic table
- Arranged horizontally in order of increasing atomic number and vertically in order in order or electron shell configuration.
- Elements in the same periods have their outermost electrons in the same shell.
- Elements in the same group have the same number of outer shell electrons (therefore similar chemistry)
Atomic radius, ionisation energy and electronegativity of an element depend on what
- Core change of outermost electrons
- Average distance of outermost electrons to nucleus
Core change:
- The effective positive charge experienced by the outermost electrons in an atom.
- Electrons in the inner shells of an atom are thought to have a shielding effect of the positive charge of the nucleus.
- Within each group, core charge attracting outermost electrons will be approximately the same.
Formula for core change
Core charge = #protons in nucleus - #inner shell electrons
Define ionisation energy
Energy required to remove an electron from an atom or an ion.
The first ionisation energy of an element is defined as the energy required to remove the outermost electron from one mole of the element in its gaseous state.
What does atomic radius depend on?
- # electrons in the atom
- shells in which electrons are located
- charge on nucleus
Atomic radius increasing and decreasing
- Increases down a group
- Decreases across a period
First ionisation energy
- Decreases down a group & increases across a period
- Can explain why some atoms lose electrons to form ions more easily than others
Electronegativity:
- The electron-attracting power of an atom in a molecule (also applied to ionic compounds and metals)
- Increases across a period (atoms smaller / core charge increases)
- Decreases down a group (atoms larger / core charge is the same)
Define bonding capacity
Bonding capacity of an atom, meaning how many spaces it has left in its valence shell
(E.g. Carbon has 4 open spaces left)
Define metallic nature
The metallic character of an element can be defined as how readily an atom can lose an electron. From right to left across a period, metallic character increases because the attraction between valence electron and the nucleus is weaker, enabling an easier loss of electrons.
