Chemistry all objectives

What is the definition of an element compound atom molecule atomic number mass number and isotope

An element is a pure substance made of one type of atom compound is two or more elements chemically combined atom is the smallest particle of an element molecule is two or more atoms bonded together atomic number is the proton count mass number is protons plus neutrons and isotopes are atoms of the same element with different neutron counts

How is the structure of an atom described using nucleus and electron cloud or shells

An atom consists of a dense central nucleus containing protons and neutrons surrounded by electrons moving in energy shells or an electron cloud

What are the location relative mass and relative charge of protons neutrons and electrons

Protons are located in the nucleus with a relative mass of 1 and charge of +1 neutrons are in the nucleus with a relative mass of 1 and charge of 0 and electrons are in shells with a relative mass of 1/1840 and charge of -1

How is atomic structure notation A/Z E used to identify atomic number Z and mass number A

Z represents the atomic number or number of protons while A represents the mass number or total protons plus neutrons

What is the definition of isotopes and what are examples

Isotopes are atoms of the same element with identical atomic numbers but different mass numbers due to varying numbers of neutrons such as Carbon-12 and Carbon-14

How do you write the correct notation for an isotope of an element

Write the element name or symbol followed by a hyphen and its mass number such as Carbon-12 or C-12

How do you determine the number of protons neutrons and electrons in an isotope

Protons equal the atomic number Z electrons equal Z in a neutral atom and neutrons equal A - Z

How are electrons arranged around the nucleus for the first 20 elements in Bohr's model

Electrons fill energy shells outward from the nucleus in maximum capacities of 2 in the first shell 8 in the second 8 in the third and 2 in the fourth

How do you write the electron configuration for the first 20 elements

List the number of electrons in each occupied shell separated by commas such as Carbon with atomic number 6 written as 2

What are valence electrons and the valence shell

Valence electrons are the electrons located in the outermost occupied shell which is called the valence shell

How do valence electrons relate to group numbers and chemical properties

The number of valence electrons equals the main group number and determines how an element reacts chemically

Where are metals and non-metals located on the periodic table

Metals are located on the left and center while non-metals are located on the upper right side

How is the periodic table arranged with reference to atomic number

Elements are arranged in order of increasing atomic number

Where are alkali metals alkaline earth metals transition metals halogens and noble gases located

Alkali metals are in Group 1 alkaline earth metals are in Group 2 transition metals are in groups 3 to 12 halogens are in Group 17 and noble gases are in Group 18

What is the link between valence electrons and group number as well as electron shells and period number

Valence electrons equal the main group number and the total number of occupied electron shells equals the period number

Why do elements in the same group have similar chemical properties

They have the same number of valence electrons in their outer shell

How do metallic bonds form

Metallic bonds form from the strong electrostatic attraction between a lattice of positive metal cations and a sea of delocalised valence electrons

What is the structure of metals

A 3D crystalline lattice of fixed positive metal ions surrounded by mobile delocalised electrons

Why do metallic substances have high melting points malleability ductility and electrical conductivity

High melting points are due to strong electrostatic attraction throughout the lattice malleability and ductility occur because layers of ions slide over each other without breaking bonds and electrical conductivity is due to mobile delocalised electrons carrying charge

What is an ion and why do ions form

An ion is an atom that has gained or lost valence electrons to achieve a stable full outer shell resulting in an overall electric charge

How do you write and identify ions from atomic structure notation

A loss of valence electrons forms a positively charged cation (+) and a gain of valence electrons forms a negatively charged anion (-)

What are the symbols names and valencies of common ions

Monatomic ions lose or gain electrons based on group number while polyatomic ions retain set formulas and charges like hydroxide (OH-)

How do you write the name and formula for ionic compounds

Name the metal cation first followed by the non-metal anion ending in -ide and balance total positive and negative charges to zero

How do ionic bonds form

Ionic bonds form when a metal atom transfers valence electrons to a non-metal atom forming oppositely charged ions that attract

What is the structure of ionic compounds in solid liquid and aqueous states

Solids form a rigid 3D ionic lattice liquids have free-moving dissociated ions after melting and aqueous states contain dissociated ions surrounded by water molecules

Why do ionic substances have high melting points and state-dependent electrical conductivity

High melting points are due to strong ionic bonds throughout the lattice and they conduct electricity in liquid or aqueous states because ions are free to move but cannot conduct in solid state because ions are held in fixed positions

How do covalent bonds form

Covalent bonds form when non-metal atoms share pairs of valence electrons to achieve full outer shells

What is the structure of covalent molecular substances

Individual molecules held together internally by strong covalent bonds but bound to neighboring molecules by weak intermolecular forces

Why do covalent molecular substances have low melting points and poor electrical conductivity

Low melting points are due to weak intermolecular forces that require little heat energy to break and poor conductivity is due to the absence of free-moving ions or charged particles

What are the common chemical formulas for ammonia water hydrogen peroxide hydrogen sulphide chlorine nitrogen hydrogen oxygen fluorine bromine and iodine

Ammonia is NH3 water is H2O hydrogen peroxide is H2O2 hydrogen sulphide is H2S chlorine is Cl2 nitrogen is N2 hydrogen is H2 oxygen is O2 fluorine is F2 bromine is Br2 and iodine is I2

What is collision theory

Collision theory states that chemical reactions occur only when reacting particles collide with sufficient energy equal to or greater than activation energy and with correct molecular orientation

How do surface area temperature and concentration affect reaction rate according to collision theory

Increasing surface area or concentration increases collision frequency while increasing temperature increases collision frequency and the proportion of particles with energy exceeding activation energy

How do you write balanced chemical equations with state symbols

Ensure equal numbers of each atom on both sides of the equation and append solid (s) liquid (l) gas (g) or aqueous (aq) to each compound

How do you identify ionic solids as soluble or insoluble using a solubility table

Check the solubility rules where nitrates and group 1 compounds are soluble and insoluble combinations form a solid precipitate

How do you write balanced molecular and ionic equations for precipitation reactions

Molecular equations show full formulas ionic equations show all dissolved ions separated and net ionic equations retain only the ions forming the insoluble solid precipitate

What are the definitions of acids bases and salts

Acids produce hydrogen ions (H+) in solution bases accept hydrogen ions or produce hydroxide ions (OH-) and salts are ionic compounds formed when the hydrogen of an acid is replaced by a metal cation

What are the chemical formulas for hydrochloric acid nitric acid sulfuric acid phosphoric acid ethanoic acid and carbonic acid

Hydrochloric acid is HCl nitric acid is HNO3 sulfuric acid is H2SO4 phosphoric acid is H3PO4 ethanoic acid is CH3COOH and carbonic acid is H2CO3

Which chemicals are classified as bases

Metal oxides metal hydroxides metal carbonates metal hydrogen carbonates and ammonia

What is neutralisation

A chemical reaction in which an acid reacts with a base to produce a salt and water

What are the products of acid reactions with metal hydroxides carbonates and metals

Acid plus metal hydroxide forms salt and water acid plus metal carbonate forms salt water and carbon dioxide gas and acid plus metal forms salt and hydrogen gas

What is Avogadro’s number and how does it define one mole

Avogadro's number (NA = 6.022 x 10^23) represents the exact number of particles present in one mole of any substance

What is molar mass and how is it calculated

Molar mass (M) is the mass of one mole of a substance expressed in grams per mole (g/mol) calculated by adding the atomic masses of all constituent atoms

What are the formulas used for mole calculations

n = N / NA to convert particle count to moles and n = m / M to convert mass in grams to moles

How do you use mole ratios in stoichiometric calculations

Use the balanced chemical equation coefficients to relate known moles to unknown moles using the ratio Moles (Unknown) = Moles (Known) x [Coefficient (Unknown) / Coefficient (Known)]