Unit 2 Flashcards
What is Dalton’s model of an atom?
- Composed of particles called atoms
- Cannot be destroyed or created
- Atoms of the same elements are identical
- Atoms of different elements combine in small numbers to form molecules
What are electrons?
- Different metals produce a stream of negatively charged particles when voltage is high
- Displayed negative electrons suspended in positively charged substances
What are features of a nucleus?
- Atoms are mainly space
- Nucleus contained most of the mass of atom
- Electrons surround the nucleus
What are subatomic particles?
Nucleus contains subatomic particles called protons, neutrons and most mass of atom, electrons occupy space outside of nucleus.
What are ions?
Atoms lose or gain electrons to form ions
What are cations?
Positive ions formed by loss of one or more electrons
What are anions
Negative ions formed by gain of one or more electrons
What are isotopes and its properties?
Isotopes are elements with the same number of protons but different number of neutrons. They have:
- Same chemical properties as parent element since neutrons don’t affect how they react
- Isotopes with more neutrons heavier and slower
- Difference in neutrons affects physical properties such as boiling, melting points, density and rate of diffusion
What is the use of carbon 12?
Since masses of elements range, difficult to manage using relative values thus standard agreed upon.
Carbon 12 chosen as relative mass exactly 12g, thus other elements measured relative to Carbon 12 isotope.
What are atoms?
Smallest particles that retain of the element, they have nucleus and space around nucleus where electrons are located
What is a electromagnetic spectrum?
The electromagnetic spectrum is a range of frequencies that covers all electromagnetic radiation and their respective wavelengths and energy
It is divided into bands or regions, and is very important in analytical chemistry.
The spectrum shows the relationship between frequency, wavelength and energy2
What is emission spectrum?
When electrons energy increases, electrons jump to a higher level but can also be reversible and return to original energy levels results in frequency being same but as its emitted and not absorbed
Energy emitted is mixture of different frequencies which corresponds to possibility of electron jumps between energy shells.
What is continuous spectrum?
A continuous spectrum in the visible region contains all the colors of the spectrum
This is what you are seeing in a rainbow, which is formed by the refraction of white light through a prism or water droplets in rain
What is line spectrum?
a line spectrum only shows certain frequencies, This tells us that the emitted light from atoms can only be certain fixed frequencies with each line representing a specific energy level
What is the hydrogen spectrum?
Hydrogen atoms give out energy when electrons falls from higher to lower energy levels
Hydrogen produces visible light when electrons falls to second energy level
What region is n=1 level?
UV region
What regions is n=2 level?
Visible light
What region is n=3 level?
Infrared
What are rules and principles of electronic configurations?
- Electrons enter lowest available energy level
- 2 electrons in each orbital, providing they are opposite spin
- Placing 2 electrons in one orbitals means both negatively charged, thus electrostatic combustions present which places electrons on separate orbital reducing repulsion and system become more stable.
What are properties of shells?
Electrons are arranged in electron shells with shells having sub shells. Each shell made up of electron orbitals each holding 2 electrons.
What are properties of orbitals?
Each level consist of electron orbitals, each holding 2 electrons with opposite spin. Orbitals are regions of space that electrons are most likely to be in.
What is afbau principle and level of energy shells?
When electrons enter orbital at lowest energy orbital available, Order is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4d etc
What is hund’s rule for electron orbitals?
Electrons occupy orbitals on own, they only pair up when no empty orbitals of the same energy available. Arrows represent opposite spins and are in up or down direction.
How are ions formed?
Ionic bonds involve transfer of electrons from metal to non metal, transferring electrons leaves metal and non metal with full outer shell
What is ionic bonding?
Forces of attraction between oppositely charged ions, cations and anions oppositely charged thus attract each other and forms ionic compounds, forms of attract very strong and requires lots of energy to overcome.
What are binary ionic compounds?
Composed of ions of 2 different element, consists of cation and anion.
Ex: Sodium Iodide
What are the charges of ionic compounds?
They are electrically neutral as positive charges equal negative charges meaning overall change is zero
What are charges of positive metal ions?
- Metals form positive ions
- Metals in group 1, 2 and 3 have charge of 1+, 2+ and 3+
- Charge on transition elements shown through roman numerals
What are charges of negative nonmetal ions?
- Non metals in group 6 to 8 have negative charge and suffix ide, elements in group 6, 7, 8 have charges 1-, 2- and 3-
What are polyatomic ions?
Negative compounds ions made up of more than one type of atom, generally negative but can be positive
What are the seven polyatomic ions?
- Ammonium (NH4+)
- Hydroxide (OH-)
- Nitrate (NO3-)
- Hydrogen carbonate (HCO3-)
- Carbonate (CO3 2-)
- Sulfate (SO4 2-)
- Phosphate (PO4 3-)
How does nuclear charge work?
- Increases as you move across periodic table
- Nuclear charge of outer electrons less than full nuclear charge
- Effective charge increases with nuclear charge as no change in inner electrons
- As you go down the group, effective charge stays the same
How do ionization energies work for elements in periodic table?
Elements with lower ionization energies form positive ions, ionization decreases down the group.
What are ionic lattices?
Ionic compounds form ionic lattices, evenly distributed crystalline structures.
Ions in lattice arranged in regular pattern so that positive charges cancel out negative charges.
They are arranged in repeating pattern.
What forces hold ionic lattices together?
Consists of alternating cations and anions thus electrostatic forces of attraction between oppositely charged ions.
What is lattice enthalpy?
Lattice dissociation enthalpy is standard enthalpy change that occurs on formation of 1 mole of gaseous ions from solid lattice, endothermic process so enthalpy change will be positive value.
What are properties of ionic compounds (Melting point, volatility, solubility, conductive) ?
- Strong electrostatic forces in ionic compound keeping ions together
- Brittle as ionic compounds can split apart
- High melting and boiling point due to electrostatic attractions in all directions to keep strongly together
- Not volatile, lots of energy needed to overcome strong electrostatic attractions
- Soluble in water as they form ion dipole bonds
- Conducts electricity when molten or in solutions as ions freely move, cannot in solid as electrons in fixed position and cannot move.
What are covalent bonds?
- Bonding between 2 non metals, involves electrostatic attractions between 2 nuclei at 2 atoms and electrons of their outer shells.
- Electrons only shared in types of bonding where 2 atomic orbitals and molecular orbitals formed
Why does covalent bonding occur?
Electrons become more stable when attracted to 2 nuclei compared to only one and when elements have full outer shell.