SC4 - The Periodic Table ✓

Question 1

SC4a - How did Mendeleev organise his periodic table?

Answer 1

By increasing atomic mass

Question 2

SC4a - How did Mendeleev predict the property of elements such as eka-alluminium (now known as gallium)

Answer 2

He identified the trend in properties down a group and used this information to estimate the properties of undiscovered elements

Question 3

SC4a - What two things did Mendeleev do to the order of elements in his table that made it more sucessful than others?

Answer 3

• Left gaps for certain elements
• Swapped elements around
• He did this because he realised a trend in the chemical and physical properties in relation to the groups of elements

Question 4

SC4b - Compare and Contrast Mendeleev’s periodic table and the Modern Periodic Table

Answer 4

• Mendeleev’s table ordered elements in increasing relative atomic mass whereas the modern periodic table orders elements in increasing atomic number
• On Mendeleev’s table there were only around 50 known elements whereas the modern table has around 100 known elements.
• Mendeleev switched the position of some elements so they were with other elements of similar chemical properties whereas in the modern table elements are grouped in columns with similar chemical properties.
• Mendeleev predicted the existence of some elements so left gaps for them in his table, these elements were discovered. There are still some other gaps in the modern table for more undiscovered elements.

Question 5

SC4b - How is the atomic number related to energy given off in x-rays when electrons are fired at an element?

Answer 5

• The square root of the energy given off is directly proportionate to the atomic number.
• This realisation proved the idea of protons and that the atomic number is the number of protons in an atom.

Question 6

SC4b - What are the four main features of the modern periodic table?

Answer 6

• Elements in a period are in order of increasing atomic number
• Elements with similar properties are in the same group
• Non-metals are on the right and metals are on the left
• The Iodine Tellerium pair reversal is explained

Question 7

SC4b - Why does (in the modern periodic table) Tellerium come before Iodine despite having a greater mass number?

Answer 7

• Iodine exists mostly as Iodine-127
• Tellerium has many isotopes ranging from Te-126 to Te-130
• This means Tellerium’s Ar is ~128
• This proves one reason why it is more reliable to order elements by increasing atomic number than by mass number

Question 8

SC4c - How do atoms store electrons?

Answer 8

• Atoms have electrons in orbits of electron shells around the nucleus
• The first shell holds up to 2 electrons
• The second and third shell holds up to 8 electrons

Question 9

SC4c - How do you work out the electron configuration of an element? Use Chlorine (Atomic number 17) as an example

Answer 9

• Atomic number 17 means 17 protons and thus 17 electrons. 1
• 7-2 is 15, 15-8 is 7, 7-8 is a negative number so there are 2 in the first shell,8 in the second and 7 in the third 2.8.7

Question 10

SC4c - How does the electron configuration of an atom relate to its position on the periodic table in terms of group and period?

Answer 10

• The total amount of electron shells will be the period it is in.
• The number of electrons in its outermost shell is equal to the group that it’s in.