Atomic Structure and Isotopes & 2.1.2 Compounds, Formulae and Equations Flashcards
What was stated in Dalton’s atomic theory?
- Atoms are tiny particles made of elements
- Atoms cannot be divided
- All atoms in an element are the same
- Atoms of one element are different from those of other elements.
What did Thompson discover about electrons?
- They have a negative charge
- They can be deflected by a magnet and electric field
- They have a very small mass.
Explain the plum pudding model.
Atoms are made up of negative electrons moving around in a sea of positive charge.
What were Rutherford’s proposals after the gold leaf experiment?
- Most mass and positive charge are in the nucleus
- Electrons orbit the nucleus
- Most of the atom’s volume is the space between the nucleus and electrons
- Overall positive and negative charges must balance.
Explain the current model of the atom.
- Protons and neutrons are found in the nucleus
- Electrons orbit in shells
- Nucleus is tiny compared to the total volume of the atom
- Most of the atom’s mass is in the nucleus
- Most of the atom is empty space between the nucleus and electrons.
What is the charge of a proton?
1+
What is the charge of an electron?
1-
Which particle has the same mass as a proton?
Neutron
Which two particles make up most of the atom’s mass?
- Protons
- Neutrons
Which letter is used to represent the atomic number of an atom?
Z
What does the atomic number tell about an element?
- Number of protons in an atom.
Which letter represents the mass number?
A
How is mass number calculated?
Mass number = Number of protons + Number of neutrons
How to calculate the number of neutrons?
Number of neutrons = Mass number - Atomic number
Define isotope.
Atoms of the same element with a different number of neutrons.
Why do different isotopes of the same element react in the same way?
- Neutrons have no impact on chemical reactivity
- Reactions involve electrons, and isotopes have the same number of electrons in the same arrangement.
What are ions?
Charged particles formed when an atom loses or gains electrons.
What is the charge of the ion when electrons are gained?
Negative
What is the unit used to measure atomic masses called?
Unified atomic mass unit (u)
Define relative atomic mass.
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom.
What is the unit of relative atomic mass?
No units.
Define relative isotopic mass.
The mass of an atom of an isotope compared with one-twelfth of the mass of a carbon-12 atom.
The relative isotopic mass is the same as which number?
Mass number.
What assumptions are made when calculating mass number?
- Electron contribution is neglected
- Mass of both proton and neutron is taken as 1.0 u.
How to calculate the relative molecular mass and relative formula mass?
Both can be calculated by adding the relative atomic masses of each atom making up the molecule or formula.
What are the uses of mass spectrometry?
- Identify unknown compounds
- Find relative abundance of each isotope
- Determine structural information.
How does a mass spectrometer work?
- Sample is made into positive ions
- Ions pass through apparatus and are separated by mass-to-charge ratio
- A computer analyzes data and produces a mass spectrum.
How is the group number related to the number of electrons?
Group number = Number of electrons in the outer shell.
Does the group number indicate a horizontal or vertical column in the periodic table?
Vertical column.
Do metals usually gain or lose electrons?
Lose electrons.
Which are the four elements that don’t tend to form ions and why?
- Beryllium
- Boron
- Carbon
- Silicon
- Requires a lot of energy to transfer outer shell electrons.
What are molecular ions?
Covalently bonded atoms that lose or gain electrons.
What is the charge of an ammonium ion?
+1 (NH₄⁺)
What is the charge of a hydroxide ion?
-1 (OH⁻)
What is the charge of a nitrate ion?
-1 (NO₃⁻)
What is the charge of a carbonate ion?
-2 (CO₃²⁻)
What is the charge of a sulfate ion?
-2 (SO₄²⁻)
What is an empirical formula?
The simplest whole number ratio of atoms in a compound.
How to calculate an empirical formula?
- Divide the amount of each element by its molar mass
- Divide the results by the smallest value obtained
- If there’s a decimal, divide by a suitable number to make it whole.
