Atoms And Molecules Flashcards
What is an atom
-Smallest unit of matter that still retains the properties of an element
-is composed of 3 subatomic particles:proton,neutron,electron
Where are protons,neutrons,and electrons found
Protons and neutrons make up the nucleus of the atom, a dense and positively charged core, whereas the negatively charged electrons can be found around the nucleus in an electron cloud.
What is the mass number
Number of protons+number of neutrons
Daltons
-Unit off measurement used for atoms and subatomic particles aswell as molecules
-its the same as the atomic mass unit
How many daltons are masses of neutrons and protons
Close to 1
Why is mass of electron not included in the atomic mass
It’s only about 1/2,00 of a neutron or proton therefore it can be ignored
Electron cloud model Schrödinger 1926
-Model Represents the 2 electrons as a cloud of negative charge as a result of their motion around the nucleus
-nucleons in the centre
Bohr model 1913
-electrons are spheres around the nucleus
-protons have a positive charge and determine the element
-neutrons have no charge and determine the isotope
Element
any substance that cannot be broken down to any other substances by chemical reactions
Compound
is a substance consisting of two or more different elements combined in a fixed ratio
Isotopes
-All atoms of a given element have the same number of protons, but some atoms have more neutrons than other atoms of the same element and therefore have greater mass(same number of protons but a different number of neutrons.)
-behave identically in chemical reactions
Carbon isotopes
• Both 12C and 13C are stable isotopes, meaning that their nuclei do not have a tendency to lose subatomic particles, a process called decay.
• The isotope 14C is unstable, or radioactive.
A radioactive isotope is one in which the nucleus decays spontaneously, giving off particles and energy.
• When the radioactive decay leads to a change in the number of protons, it
transforms the atom to an atom of a different element.
How is atomic mass calculated due to different isotopes
It’s the average of the different isotopes
Alpha decay
the nucleus loses two protons.
Beta decay
the nucleus either loses or gains a proto
Gamma decay
no change in proton number occurs, so the atom
does not become a different element
Radioactive Tracers
-used as diagnostic tools in medicine.
-The radioactive isotopes are incorporated into biologically active molecules, which are then used as tracers to track atoms during metabolism, the chemical processes of an organism.
-can be used with PET scanners to monitor growth and metabolism of cancers
Valence
The bonding capacity of a given atom; the number of covalent bonds that an atom can form, which usually equals the number of unpaired electrons in its outermost (valence) shell.
Valance electron
An electron in the outermost electron shell
Valence shell
The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.
Electronic configuration
• An electron’s energy level is correlated with its average distance from the nucleus.
• Electrons are found in different electron shells, each with a characteristic average distance and energy level.
Electron orbitals
Watch YouTube videos
Chemical behaviour
• The chemical behaviour of an atom depends mostly on the number of electrons in its outermost shell.
• Atoms with the same number of electrons in their valence shells exhibit similar chemical behaviour.
-group 7 is unreactive as they have a full outer shell
Types of chemical bonds
• Covalent bonds
•Electronegativity
• Ionic bonds
Covalent bond
A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.
Examples:h2,o2,h2o,ch4
Electronegativity
The attraction of a given atom for the electrons of a covalent bond.
Non-polar covalent bond:
A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
Polar covalent bond
A covalent bond between atoms that differ in electronegativity.The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
Ionic bond
Ionic bond: A chemical bond resulting from the attraction between oppositely charged ions.(cation and anion)
Ions
An atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge.
Weak chemical interactions
Hydrogen bonds
Van der waals interactions
Hydrogen bonds
Hydrogen bond: A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.
Van der waals interactions
-are dipole-dipole interactions, which commonly exist in gases, liquids, and solids.
-3 types:
- Dipole-dipole interactions(strongest)
- Dipole-induced dipole interactions
- London dispersion forces
What are dipoles
are a set of separated charges within an atom/molecule
Dipole-dipole interactions
are the attractive/repulsive forces that exist between two polar
molecules (molecules with a permanent dipole).
Dipole-induced dipole interactions
are the attractive/repulsive forces between a polar
molecule and an atom/molecule with an induced dipole.
London dispersion forces
are the attractive/repulsive forces between a nonpolar atom/molecule with an instantaneous dipole and a nonpolar atom/molecule with an induced dipole.
