An argument named "root_block_device" is not expected here

ERROR: An argument named “root_block_device” is not expected here. Did you

│ mean to define a block of type “root_block_device”?

Version : Terraform v1.0.5

My Configuration looks like :

provider “aws” {
profile = “default”
region = “eu-west-1”
}
resource “aws_instance” “app_server” {
ami = “ami-0a8e758f5e873d1c1”
instance_type = “t2.micro”
root_block_device = [{
volume_type = “gp2”
volume_size = 10
}]
tags = {
Name = “ExampleAppServerInstance”
}
}

Any Help please i get stuck here.

Answering to my own Question.

tried with below and it was fine.

root_block_device {
volume_type = “gp2”
volume_size = 250
}