Sub-atomic particles and isotopes Flashcards
What is the relative charge of proton, neutron and electron?
Proton: 1 +
Neutron: 0
Electron: 1-
What is the relative mass of proton, neutron and electron?
Proton: 1
Neutron: 1
Electron: 1/1840
Where is the location of proton, neutron and electron?
Proton: Nucleus
Neutron: Nucleus
Electron: in shells around the nucleus
What is the symbol off an atom?
An atom of an element, x, may be described by the nucleus notation:
Where the letter A is at the top left corner of X and Z is at the bottom left corner of X.
Z = atomic or proton number = number of proton
A = mass of nucleon number = the number protons and neutrons
An atom of fluorine has the symbol F with 19 at the top left corner and 9 at the bottom left corner? How many protons, neutrons and electrons does this fluorine have?
The atom has 9 protons, 9 electrons and 10 neutrons.
For any element, all the atoms have the same number of _______ and ____________.
For any element, all the atoms have the same number of protons and electrons.
In 1913 J.J. Thomson discovered that some elements could have atoms with different masses due to _____________. These atoms are called ___________.
In 1913 J. J. Thomson discovered that some elements could have atoms with different masses, due to different number of neutrons. These atoms are called isotopes.
What is the definition of isotopes?
Isotope are atoms of the same element, with same protons but different neutrons, thus different mass number,.
For example, a mass spectrometer trace shows that chlorine consists of two isotopes; each has a proton number of 17, but they have isotopic masses, 35 and 17 respectively. Thus atoms of chlorine-35 have ______ protons and ______ neutrons, whereas atoms of chlorine-37 have _____ protons and ______ neutrons.
Chlorine-35: 17 protons and 18 neutrons
Chlorine-37: 17 protons and 20 neutrons
Isotopes have the same __________ properties but different _______________. Why?
Isotopes have the same chemical properties but different physical quantities.
Isotopes have the same chemical properties as they have the same number of electrons, thus same number of valence electrons which will determine the result based on their same activity. Chemical properties depend on the transfer and redistribution of electrons.
However, since isotopes have different number of neutrons, they will have different masses and hence different physical properties, such as the difference in boiling and melting points.
For example, a sample of chlorine gas made up of only chlorine-37 will have a higher density, higher melting point and higher boiling point than a sample made up of only chlorine-35.
Chlorine-35 and chlorine-37 have relative isotopic masses of ______ and ________ respectively.
If a sample of chlorine consists of only chlorine-35 atoms, then its relative atomic mass (____) would be ______. If a sample of chlorine consists of only chlorine-37 atoms, its _____ would be _____. A 50:50 mixture of chlorine-35 and chlorine-37 would have an Ar of _____.
Chlorine-35 and chlorine-37 have relative isotopic masses 35 and 37 respectively.
If a sample of chlorine consists of only chlorine-35 atoms, then its relative atomic mass (Ar) would be 35. If a sample of chlorine consists of only chlorine-37 atoms, its Ar would be 37. A 50:50 mixture of chlorine-35 and chlorine-37 would have an Ar of _____.
Explain why the value of the relative atomic mass of X is not an integer.
Naturally occurring elements often consist of a mixture of isotopes would result in relative atomic mass which are not close to a whole number, since the relative atomic mass of an element represents the average mass of one atom taking into account the different isotopes and their relative abundances.
What are the two types of isotopes?
Radioactive and non-radioactive.
Isotopes were first discovered by scientists using the ____________.
Isotopes were first discovered by scientists using the mass spectrometer.
The mass spectrum shows that the sample of neon is made up of 90.90% of Ne-20, 0.30% of Ne-21, and 8.80% of Ne-22.
What is the average mass of a Ne atom?
The average mass of a Ne atom is
= 90.90/100 x 20 + 0.30/100 x 21 + 8.80/100 x 22 =20.179
An element X has two isotopes: 238 (at the top left corner of X) X and 235 (at the top left corner of X) x. How does 238 X differ from 235 X?
A It has 3 more protons and 3 more electrons.
B It has 3 more protons, but no more electrons.
C It has 3 more neutrons and 3 more electrons.
D It has 3 more neutrons, but no more electrons.
D
Isotopes means same element—> same element means same proton means same electron unless it is an ion.
The relative abundance of the three isotopes of magnesium is given in the table.
Isotope
Mg-24 79 (relative abundance in %)
Mg-25. 10 (relative abundance in %)
Mg-26. 11 (relative abundance in %)
Based on the given data, which one of the following expressions gives the correct calculation of the relative atomic mass of magnesium?
A (79+ 10 + 11)/100 x (24 + 25 + 26)/3
B (79 + 24) x (10 + 25) x (11 + 26) whole thing divide by 100
C (79 x 24) + (10 x 25) + (11 x 26) whole thing divide by 100 x 3
D (79 x 24) + (10 x 25) + (11 x 26) whole thing divide by 100
D
A is wrong because you can’t simply add all the fractions with divide by 100 because you need to times them first
What do both an atom and an ion of sodium 23 (left top corner) 11 (bottom left corner) Na, contain?
A 11 electrons
B 12 neutrons
C 23 protons
D 23 neutrons
B
Which statement about an atom is true?
A All the elements have only one nucleon (mass) number.
B The nucleon number can be less than the proton (atomic) number.
C The nucleon number can equal the proton number.
D The number of neutrons never equals the number of electrons.
C
The following 4 statements come from Dalton’s Theory of Atoms of 1661. The first discovery of isotopes in 1912 directly contradicts which statement?
A All matter is made of atoms, which is indivisible.
B All atoms of a given element are identical in mass and properties.
C Compounds are combinations of two or more different types of atoms in definite ratio.
D A chemical reaction is a rearrangement of atoms.
B
The atomic number of potassium is 19. The electronic structure of the potassium ion can be represented as
A 2,8
B 2,8,8
C 2,8,9
D 2,8,8,1
B
There is a contradiction between Millikan’s unqualified statement that he has published all the oil-drop data and the evidence of unpublished oil-drop measurements in his notebooks. Do you think he was guilty of unethical scientific behaviour? Why?
Yes, he should have reported that there were more data collected than those repeated by these were discarded because they were not done under optimum conditions.
If Millikan had not claimed to have published all the data, would he still be guilty of questionable behaviour?
No, if he was able to justify the discarding of some of the data reasonably and not because the data did not fit his “preconceptions” or theory.
Should the fact that Millikan was a highly successful scientist, and that he got the right answer in the controversy about the charge on the electron be a consideration in judging his scientific ethics?
No, no one should be considered above the standard just because of past experience/success. Not getting the correct answer does not justify the means by which it is obtained.
What criteria should be used in deciding whether data can be legitimately discarded?
Data collected is not properly controlled (e.g. data collected in earlier experiments compared to those in later experiments that are done with more experience and thought. Large sampling of data resulting in an accurate average value. Any deviation from this average (out-livers) can be reasonably discarded.
What is a covalent bond?
A covalent bond occurs when two atoms share electrons from heir outermost shell. Usually, each atom contributes one electron, so one covalent bond constitutes two electrons. (The word usually means that sometimes it may not be the case)
What are covalent substances?
Covalent substances can be made up of units of small molecules (each molecule may be made up of 2 to more than 50 atoms) or can be a single giant unit made up of billions of atoms.
What are the two ways in which covalent bonding can occur?
- between atoms of the same element (non-metals)
- between atoms of different elements
Molecules can have ____ covalent bonds (___ pair of electrons) between atoms, as with hydrogen, H-H and chlorine, Cl - Cl. There may be _______ bonds like 2 oxygen atoms sharing __ pairs of electrons between them O=O). A nitrogen molecule has a______ bonds between the 2 nitrogen atoms.
All these are examples of ________.
Molecules can have single covalent bonds (one pair of electrons) between atoms, as with hydrogen, H-H and chlorine, Cl - Cl. There may be double bonds like 2 oxygen atoms sharing 2 pairs of electrons between them O=O). A nitrogen molecule has a triple bonds between the 2 nitrogen atoms.
All these are examples of simple molecules.
There are two pairs of electrons on each oxygen atom and one pair of electrons on each nitrogen atom not shared or not involved in bonding. These are called ________________.
These are called lone pairs of electrons.
There are structures which comprise a very large number of atoms joined by covalent bonds. An example is ______, which is made up of carbon atoms.
An example is diamond.
A piece of diamond may be considered a ________. Each carbon is bonded to ___________. All of the covalent bonds are _______. The diagram shows the ____________ of diamond. (Think of the structure of diamond)
This explains why diamond has a ___________ and is a ____________.
A piece of diamond may be considered a giant molecule. Each carbon is bonded to four other carbon atoms. All of the covalent bonds are strong bonds. The diagram shows the giant covalent lattice structure of diamond. (Think of the structure of diamond)
This explains why diamond has a very high melting point and is a hard and rigid solid.
What are some examples of covalent bonding that occur between atoms of different elements that involve 2 atoms, 3 atoms, more than 3 atoms or thousands of atoms?
2 atoms (hydrogen chloride, HCl)
3 atoms (carbon dioxide, CO2)
More than 3 atoms (ammonia, NH3, methane, CH4, and glucose C6H12O6),
Thousands of atoms (silicon dioxide SiO2, also an example of a giant molecule.
In molecules such as carbon dioxide and ammonia, there is ____________. The __________ is the element with the least number of atoms in the molecule.
In molecules such as carbon dioxide and ammonia, there is one central atom. The central atom is the element with the least number of atoms in the molecule.
What is the difference between simple molecular structure or giant covalent structure?
In terms of the structure, simple covalent substances are made up of molecules. These molecules are bonded together by a shared pair of electrons which forms the strong covalent bond. Between molecules, weak intermolecular forces hold the molecules in either a solid, liquid or gaseous arrangement. In order to melt/boil simple covalent substances, only the weak intermolecular forces have to be overcome, which requires little energy. As a result, simple covalent substances generally have low melting/boiling points.
Giant covalent substances, such as diamond, contain many strong covalent bonds in 3D lattice structure. Between each carbon atom in diamond, there are 4 strong covalent bonds. In order to melt/boil diamond, a very large amount of energy is required to break these strong covalent bonds which results in very high melting/boiling points.
Substances with simple molecular structure such as _________, are made up of simple molecules and are usually ______, or _____ with _____ melting points. The molecules are held together by _________________.
Substances with giant covalent structure, such as __________, have all their atoms strongly held together by __________, thus hey are _____ with _______ melting points.
Substances with simple molecular structure such as O2, CO2, are made up of simple molecules and are usually gases or liquids or solids with low melting points. The molecules are held together by weak intermolecular forces.
Substances with giant covalent structure, such as diamond (C) and SiO2, have all their atoms strongly held together by covalent bonds in a large network, thus they are solids with high melting points.
Covalent bonding involves _____ forces of attraction.
Covalent bonding involves electrostatic forces of attraction.
Are covalent bonds strong or weak? Why or why not?
Covalent bonds are strong bonds
What is the difference between the group of covalent substances that has high melting points and the group of covalent substances with low melting points?
The difference between these two groups of covalent substances is the presence of weak intermolecular forces. These weak forces are present in covalent substances with simple molecular structure. A low amount of heat would readily break the weak intermolecular forces. Hence, similar molecular substances like ammonia and carbon dioxide have low melting and boiling points.
During melting and boiling, the molecules remain intact. The strong covalent bonds between the atoms in each molecule are not broken.
Example:
When ice melts and then water is boiled, only the intermolecular forces between t eh water molecules are broken. No covalent bonds are broken. No atoms of hydrogen or oxygen are produced.
By contrast, for covalent substances that have giant molecular structure, all the atoms are covalently and strongly bonded to each other. Melting would therefore involve breaking many covalent bonds between the atoms in the giant molecule. This requires a lot of heat. Hence, giant covalent substances like diamond and silicon dioxide have very high melting points.
When drawing dot and cross, what is something you can do to check if your drawings are accurate?
Calculate the valence electrons for the substance and check if the dot and cross adds up to that number
Draw a diagram to show the arrangement of the molecules when solid iodine melts. [Although solid iodine sublimes easily when heated, under certain conditions it can form liquid].
Draw two circles join by one line since it is I2 (Iodine) space multiple iodine molecules farther away as compared to when it is a solid. You can draw some Intermolecular forces of attraction by drawing dotted lines but do not draw all the intermolecular forces of attraction since some of it is already broken by the heat.
Ionic and covalent bonding are two extreme models of the chemical bond. Most actual bonds lie somewhere______________.
Most actual bods lie somewhere between purely ionic and purely covalent.
What is electronegativity?
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.
What is an example of electronegativity?
For instance, when O and H for a covalent bond, O, being more electronegative (O2-), pulls the shared electrons toward itself, creating a partial negative charge. This leaves the H with a partial positive charge. The result is a polar covalent bond.
Does metals or non-metals have higher electronegativity?
Non-metals have high of electronegativity.
__________ is most commonly used as a measure of the electronegativity of an atom.
The Pauling scale
What happens if two atoms of equal electronegativity bond together?
Consider a bond between two atoms, A and B. If the atoms are equally electronegative, both have the same tendency to attract the bonding pair of electrons, and so they will be found on average half way between the two atoms. To get a bond like this, A and B would usually have to be the same atom. You will find this sort of bond in, for example H2 or Cl2 molecules.
This sort of bond could be thought of as being “pure” covalent bond-where the electrons are shared evenly between the two atoms.
Since an atom is so small it is not practical to measure its mass in kilograms or even nanograms and to use it for calculations. True or false.
True
Since an atom is so small it is not practical to measure its mass in kilograms or even nanograms and to use it for calculations, scientists thus use the _______. ________ is about comparing the _______ of atoms and molecule. It does not have a __________.
Scientists thus use the relative mass. Relative mas is about comparing the masses of atoms and molecules. It does not have a unit.
In the earliest experiments, the ______ atom was used as a reference for other atoms’ masses.
For example, as one nitrogen atom is _______ times heavier than a hydrogen atom, nitrogen is said to have a relative atomic mass of 14.
As hydrogen, __________, is difficult to handle, scientists turn to another atom, the ______ atom. Thus today, the reference is ___________ the mass of a _________atom.
In other words, a nitrogen atom is ____ times as heavy as _______ of the carbon-atom.
In the earliest experiments, the hydrogen atom was used as a reference. Hence, the masses of all other atoms were measured against that of hydrogen.
For example, as one nitrogen atom is 14 times heavier than a hydrogen atom nitrogen is said to have a relative atomic mass of 14.
As hydrogen, being a gas, is difficult to handle, scientists turn to another atom, the carbon atom. Thus, today, the reference is one-twelfth the mass of a carbon-12 atom.
In other words, a nitrogen atom is 14 times as heavy as 1/12 of the carbon-12 atom.
What is the relative atomic mass of an element (A subscript r)?
(Average mass of one atom of the element)/ (mass of 1/2 of an atom of carbon-12)
How do you know the relative atomic mass of the elements?
In the periodic table, look at the number below each of the elements.
What is the definition of relative molecular mass (M subscript r)?
The relative molecular mass (M subscript r) of a molecule is the sum of the relative atomic masses of the atoms in the molecule.
Given that the Ar of H = 1, and that the Ar of O = 16, what is the Mr of H2O?
Mr of H2O = 1+ 1 + 16 = 18
For substances not made up of molecules the Mr refers to the ______________.
Example: sodium chloride, NaCl (ionic so not molecule)
Ar of Na = 23, Ar of Cl = 35.5
What is the Mr of NaCl?
For substances not made up of molecules the Mr refers to the relative formula mass.
The Mr of NaCl = 23 + 35.5 = 58.5
Which one of the following atoms would readily form an ion with a charge of 2+?
A mass number: 12 atomic number: 6
B mass number: 16 atomic number: 8
C mass number: 24 atomic number: 12
D mass number: 31 atomic number: 15
C
atomic number refers to the number of proton
mass number or nucleon number refers to the number of protons and neutrons
Chlorine atoms and chloride ions __________.
A are chemically identical
B have the same number of electrons
C have the same number of protons
D have the same physical properties
C
The diagram shows the arrangement of electrons in a particle.
nucleus containing 7 neutrons and 7 protons.
What is this particle? [You don’t need a Periodic Table to solve this]
A Ne
B F-
C O2-
D N3-
since 7 protons–> thus 7 electrons
electronic configuration (2,5)
gain 3e - to form (2,8)
therefore D
The diagram shows the path of electrons and protons as they enter an electric field.
_______________________ +
electrons– (go up to the above line)
protons——— ( go to the line below)
________________________ -
Why do the electrons deflect (or change direction) so much more than the protons?
Analyse the diagram first:
electrons has a negative charge while protons has a positive charge therefore it changes direction to the opposite charge.
Answer the question:
Here is the main concept:
An electron has a much lower mass/ is lighter than a proton, thus it is easily deflected in the electric field.
The explanation below is wrong:
electrons are located in shells around the nucleus which is closer to an electric field as compared to the protons which are located in the nucleus. Thus, electrons are attracted to the positive part of the electric field at a faster rate than protons to the negative part of the electric field.
Why is the second explanation incorrect?
The idea that electrons are in shells around the nucleus is not relevant here.
The diagram represents free-moving electrons and protons, not those bound inside atoms.
The strength of the electric field affects free charges directly and does not depend on their previous location in an atom.
Both electrons and protons feel the same electric force (if they have equal charge magnitude), but since electrons are lighter, they move more.
The electron shell nearest to the nucleus has the lowest energy level while the electron shells further away from the nucleus have higher energy levels. True or false？
True
How many electrons are filled in the third electron shell?
USUALLY holds up to 8 electrons
How many electrons are filled in the first electron shell and the second electron shell?
the first electron shell holds up to 2 electrons while the second electron shell holds up to 8 electrons
Cl -35 and Cl - 37 are two isotopes of chlorine.
Which statements are correct?
1 Both isotopes have the same mass number.
2 Both isotopes have the same electronic configuration.
3 Both isotopes have the same physical properties.
4 Both isotopes have the same chemical properties.
2 and 4 only
Isotopes have different number of neutrons hence will have different mass number and different physical properties.
Isotopes have the same number of electrons and hence will have the same electronic configuration.
Ions are formed by the __________________ of electron(s) from typically a metal atom to typically a non-metal atom and these ions usually have the electronic configuration of a noble gas.
(A) sharing
(B) transferring
Ans: B, transferring
Feedback
Ions are formed by transferring of electron(s) from a one atom to anoter atom. Metal atoms will typically form positive ions and non-metal atoms will typically form negative ions. Both positive and negative ions will usually have the stable electronic configuration of a noble gas.
What is the formula of Manganese(IV) oxide?
MnO2 not MgO
