化学家教张老师九月份开AP化学小班，从2020年九月份到2021年五月初，学习AP化学的各方面知识，助小朋友们参加2021年五月份的AP化学考试。如果您有兴趣参加，请联系张老师：email： vancouverchemsitrytutor@gmail.com 或致电 6048086827.
Saturday, June 6, 2020
AP chemistry small group class starting Sept. 2020
Hello, this is Ling the chemistry tutor. I am planning to start a small group AP chemistry class in September 2020. The group will study all AP concepts and be prepared to take the AP Chemistry exam in May 2021. if you are interested, please send am email to vancouverchemistrytutor@gmail.com or text 6048086827 for details.
Thank you for visiting my blog.
Thank you for visiting my blog.
Wednesday, February 5, 2020
matching video for Q 69 posted on youtube
Detailed explanation of AP Chemistry Question of the Day is posted on YouTube. Check it out. The link is https://youtu.be/ihBBlbooU-E
All the best!
Ling
All the best!
Ling
Tuesday, February 4, 2020
AP Chemistry Question of the Day --69
I was reviewing atomic structure with my students and find the following question confusing to quite some people and I decided to share it here.
Which of the following transition metal ions has the most unpaired electrons?
A. Co (2+)
B. Mn (2+)
C. Zn (2+)
D. Fe (2+)
The answer is B. For transition metals electrons fills in the 4s subshell first before they fill the 3d subshell due to Aufbau Rule which states that electrons fill in orbital with lower energy first. Since 4s has lower energy than 3d, they fill in 4s first. There are 5 orbitals in 3d subshell, according to Hund's Rule, which state that electrons will fill separate orbitals before they pair up to avoid repulsions, as a result, Co has 7 electrons in 3d, 3 unpaired and 4 paired up, Mn has 5 unpaired in 3d, Zn has no unpaired in 3d and Fe has 4 unpaired and 2 paired electrons in 3d.
Now comes the tricky part, when transition metals form cations, they always lose their outmost electrons first. As a result, the 4s electrons are lost and the number of electrons remain the same as the original atoms if the charge of the ions are +2. Only when you are losing more than 2, addition electrons in 3d will be removed.
Hope this is helpful to you.
All the best!
Ling
Which of the following transition metal ions has the most unpaired electrons?
A. Co (2+)
B. Mn (2+)
C. Zn (2+)
D. Fe (2+)
The answer is B. For transition metals electrons fills in the 4s subshell first before they fill the 3d subshell due to Aufbau Rule which states that electrons fill in orbital with lower energy first. Since 4s has lower energy than 3d, they fill in 4s first. There are 5 orbitals in 3d subshell, according to Hund's Rule, which state that electrons will fill separate orbitals before they pair up to avoid repulsions, as a result, Co has 7 electrons in 3d, 3 unpaired and 4 paired up, Mn has 5 unpaired in 3d, Zn has no unpaired in 3d and Fe has 4 unpaired and 2 paired electrons in 3d.
Now comes the tricky part, when transition metals form cations, they always lose their outmost electrons first. As a result, the 4s electrons are lost and the number of electrons remain the same as the original atoms if the charge of the ions are +2. Only when you are losing more than 2, addition electrons in 3d will be removed.
Hope this is helpful to you.
All the best!
Ling
Thursday, January 9, 2020
Ksp calculations video published on YouTube
Hello, It is Ling the chemistry tutor. I posted a new video in Youtube about Ksp calculations. Check it out when you have time. the link is https://youtu.be/CQ07O1zcilk
you can subscribe to my channel Ling the chemistry tutor on YouTube.
All the best!
Ling
you can subscribe to my channel Ling the chemistry tutor on YouTube.
All the best!
Ling
Tuesday, January 7, 2020
Another video posted on YouTube on acid and base strength, Ka Kb and Kw
I posted another video on YouTube about acid and base strength, Ka Kb and Kw and also about the levelling effect of water. Check it out.
Friday, January 3, 2020
check out my first YouTube video
I just posted on YouTube my first ever chemistry tutoring video on definitions of acid and base. Check it out. The link is https://youtu.be/lCRlA1NCYmg
If you have any questions that you need help with. Let me know.
Thank you.
Ling
If you have any questions that you need help with. Let me know.
Thank you.
Ling
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