SC4a - How did Medeleev organise his periodic table?
By increasing atomic mass
SC4a - What two things did Mendeleev do to the order of elements in his table that made it more sucessful than others?
- 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
SC4a - How did Mendeleev predict the property of elements such as eka-alluminium (now known as gallium)
He identified the trend in properties down a group and used this information to estimate the properties of undiscovered elements
SC4b - Why does (in the modern periodic table) Tellerium come before Iodine despite having a greater mass number?
- 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
SC4b - How is the atomic number related to energy given off in x-rays when electrons are fired at an element?
- 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.
SC4b - What are the four main features of the modern periodic table?
- 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
SC4c - How do atoms store electrons?
- 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
SC4c - How do you work out the electron configuration of an element? Use Chlorine (Atomic number 17) as an example
- 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
SC4c - How does the electron configuration of an atom relate to its position on the periodic table in terms of group and period?